Anatomic Sciences Nuggets

ANATOMIC SCIENCES REVIEW

FACIAL VEINS LYMPH

USC messed up the following questions:

1979 Q79 (all of these structures pass through the diaphragm)

1989 - The one about which is not a branch of Celiac or its branches. It says Left gastroepiploic, answer is inferior pancreaticoduodenal. Questions I just didn’t include:

1982 Q92

CELLS - Components of cells

o Plasma MB:

 Dynamic, selectively permeable MB enclosing the cytoplasm  Between cell wall & cytoplasm

 Composition:

• Lipids (phospholipids, cholesterol, glycolipids)

o Cholesterol increases mechanical stability; also decreases MB fluidity, but prevents freezing o Increasing unsaturated FAs increases fluidity

• Proteins (integral MB proteins & peripheral MB proteins) o All transport proteins are integral MB proteins

• One layer of charged lipids on either side of a layer of neutral lipids

 Cell coat and microfilaments are attached to the cell membrane (golgi complex is not) o Cell Wall:

 Protects the cell from changes in osmotic pressure  Anchors flagellae

 Maintains shape o Fluid stuff:

 Protoplasm:

• Viscous, translucent, watery material that is a primary component of animal cells

• Contains large % water & inorganic ions (K+, Ca2+, Mg2+, Na+) & naturally occurring organic compounds (e.g., proteins) o Irritability

 Property of protoplasm responsible for cell being sensitive to a stimulus  Nucleoplasm:

• Protoplasm of the cell nucleus – plays part in reproduction • Communicates with the cytoplasm by way of nuclear pores

o Molecules < 40kD can diffuse freely between nucleoplasm & cytoplasm thru the pores  Cytoplasm:

• Protoplasm of the cell body that surrounds the nucleus, converts raw material into energy • Site of most synthesis activities

• Contains cytosol (viscous, semitransparent fluid that is 70-90% water), organelles, and inclusions (metaplasm)  Metaplasm:

• Name given to lifeless material stored in cytoplasm

• EX: glycogen (an example of a cytoplasmic inclusion), fat deposits, pigment granules—including lipofuscin (yellowish-brown substance that ↑ in quantity as cells age), and melanin (abundant in epidermis of skin & retina)

o Lipofuscin is the “wear & tear” pigment o Microtubules:

 Specialized type of filament composed of polymerized tubulin (protein)  Cylindrical hollow structures in the cytoplasm of all eukaryotic cells  Provide support and assist in cellular locomotion

 Flagella and cilia o Flagella:

 Present in humans – only in the spermatozoa  Core composed of microtubules

• 9 double circumferential microtubules and 2 single centrally located microtubules  Much longer than cilia

 Move w/ an undulating snake-like motion o Cilia:

 Short, hair-like projection from the cell MB  Beat in coordinated waves

 Core composed of microtubules

• 9 double circumferential microtubules and 2 single centrally located microtubules • 9 + 2 arrangement of microtubules

o Similarities between Flagella and Cilia:

 Nine sets of doublets, two singlets in center  Basal body

• Essential to function of cilia and flagella

• From the basal body, fibers project into the cytoplasm, possibly to anchor the basal body to the cell  Move by contraction of tubular proteins

o Axoneme:

 Characteristic 9+2 pattern

 Peripheral pairs share common wall of 2-3 protofilaments

 Central pair of tubules are separated from one another and are enclosed w/in a central (single) sheath. Doublets and central sheath linked by nexins

o CenTRIoles:

 Nine sets of triplets

 The microtubule organizing center of the cell o Centrosomes:

 Contain centrioles o Microfilaments:

 Much smaller than microtubules and have contactile and structure groups • Contractile is made up of

o Double-stranded helices of polymerized actin o Actin and myosin

• Structural is made up of

o Tonofilaments – support the cell and provide attachments for Desmosomes, which anchor contigous cells, and terminal webs , which anchor microvilli

 What layer are they found in????  are they used in hemidesmosomes at the basal layer = stratum germ/basale, I’m going with Spinosum?

• They are found in ALL layers except for corneum  This test Sucks!  Involved in local movement, by sliding filament movement (as in muscle fiber microfilaments)

o Microvilli:

 Think Microvillaments  Core of microfilaments  Intestines

 Primary purpose is to increase functional surface area (not flagella or cilia)

o ***Hey: Microvilli have microfilaments; Cilia have microtubules – don’t screw it up!!! o Stereocilia:

 Long, nonmotile microvilli that cover the free surface of some of the pseudostratified columnar epithelium which line the inside of the Epididymis

 S for Sex and Stereocilia

 Different from Cilia in that they are Nonmobile and have microvilli (microvillaments) NOT microtubules  Facilitate the passage of nutrients from the epithelium to the sperm by increasing the epitheliums surface area  Also present in the ductus (vas) deferens, which is also lined with pseudostratified epithelium

o Intermediate filaments:

 Rope-like filaments that function in structural roles o Barr body:

 Sex chromatin body

 Genetic activity of both X chromosines is essential only during the first weeks after conception • Later development only requires one functional X

• Inactivated X chromosome appearing in dense chromatin mass attached to nuclear MB of normal female  Absent in normal males

• If a male has a barr body, then he has Klinefelter’s (XXY)

 Sex of embryo determined if Barr body presence as early as eight weeks  Important in recognition in epi cells because it tells us sex

o Cytoskeletal elements:

 Form network of protein structures o Nucleus

 DNA is found principally in the nucleus

 Feulgen Reaction – test to distinguish beween DNA and RNA  Tells us what the Nucleus is FEUL full of

 Site of rRNA synthesis (not DNA, tRNA, or mRNA) • NOTE: rRNA is the most abundant RNA in the cell

 NOT bound by a membrane (unlike nucleus, lysosome, mitochondrion, & pinocytotic vesicle) o Ribosomes:

 Site of protein synthesis

 All protein synthesis begins on free polysomes o Smooth ER (ribosomes are absent):

 Steroid synthesis (vs. Protein Synthesis for RER)

• The Q reads: Smooth ER predominates in steroid producing cells, but not in protein producing cells  Protein synthesis for use inside the cell

 Intracellular transport

 Detoxification reactions (hydroxylation & conjugation)

 Glycogen degradation & gluconeogenesis (glucose-6-phosphatase is an integral MB protein of the SER)  Lipolysis begins in the SER

 Production of bile salts (when in hepatocytes)

 ***Hepatocytes & steroid hormone producing cells of adrenal cortex are rich in SER o Rough ER (ribosomes are attached):

 Protein synthesis for use outside the cell – aka, site of synthesis of secretory proteins  Also site of N-linked oligosaccharide addition to many proteins

 Think Osteoblasts

 Associated with RNA – repeated again & again & again on tests (rRNA)  *Cytoplasmic RNA is localized in granular endoplasmic reticulum  Has regions that are smooth in appearance – called transitional elements  ***Mucus-secreting goblet cells & Ab-secreting plasma cells are rich in RER  Active cells – characterized by an abundance of rough ER (fibroblasts, osteoblasts) o Golgi apparatus:

 Flat, membranous sacs or cisternae arranged in stacks (the stacks are called dicytosomes) w/ two poles • The cis face receives material

• The trans face is for transportation function

 Packages, stores, modifies & sorts products – post-translational  Packages secretory material and forms lysosomes

 Forms glycoproteins for extracellular use

 Proteoglycan assembly from proteoglycan core proteins  Modifies N-oligosaccharides on asparagine

 Adds O-oligosaccharides to serine & threonine residues (O-linked glycosylation)  Procollagen filaments formed here from polymerization of amino acids!!!!!

• Polymerization of molecules into collagen fibrils occurs in the Golgi o Lysosomes:

 Cytoplasmic MB-bound vesicles containing glycoprotein hydrolytic enzymes that digest & destroy exogenous material  Lysosomes deal w/ biochemical breakdown & phagocytosis in the oral region

 Are formed in the Golgi apparatus (they bleb off of it)  Are called to action when the cell produces too much proteins o Peroxisomes:

 Contain oxidases, enzymes capable of reducing oxygen to hydrogen peroxide and hydrogen peroxide to water  Bile acid synthesis occurs in peroxisomes

o Vacuoles:

 Store & excrete various substances w/in the cytoplasm o Glycosomes – store sugar (found in liver)

o Mitochondria:

 Threadlike structures w/in the cytoplasm that provide ATP  Similar to bacteria in shape & size

 Reproduce by dividing (also like bacteria)

 The most important organelle or component of a cell for oxidative processes = mitochondrion  Contain a double MB (inner & outer MBs)

• Outer MB:

o Smooth, continuous, permeable

o Contains a lot of porin (integral MB protein that forms channels in the outer MB) • Inner MB:

o Impermeable to small ions (due to high content of cardiolipin) o Enzymes for ETC & Oxidative Phos are embedded in the inner MB

 Both mitochondria and nucleus have double-unit membrane (not lysosome, Golgi complex, or rough ER)  Maternal DNA Link

• Contains cyclic DNA  Crista of the Mitochondria

• Stores and provides more surface area for chemical reactions to occur (Protein NZs) - Embryonically early cell types/forms:

o Mesenchymal cells (mesoblastic cells)

 Potential to proliferate & differentiate into diverse types of cells  Form a loosely woven tissue called mesenchyme or embryonic CT o Mesectoderm (ectomesenchyme)

 Derived from ectoderm, especially from the neural crest in the very young embryo  The primary source of cranial connective tissue cells is the ectomesenchyme o Neural crest cells:

 Give rise to spinal ganglia (dorsal root ganglia) and the ganglia of the ANS

 Give rise to neurolemma cells (Schwann cells), cells of the meninges that cover the brain and spinal cord, pigment cells (Melanocytes), chromaffin cells of adrenal medulla and several skeletal and muscular components of head

o Fetus Blood Cells

 Developing fetus blood cells are found in the red bone marrow, liver, spleen, and lymph nodes - Important Cells—Function or Location

o Macrophage—phagocytosis, defense against bacterial infection  Activated by gamma-IFN

 Can function as APC  Kupffer cell—liver  Splenocyte—spleen  Histiocyte—loose CT

o Mast Cells—mediators of inflammation on contact w/ antigen, same as Basophil in that it secretes Heparin & Histamine  Mediates allergic reaction – involved in type I hypersensitivity reactions

o Schwann—form myelin sheath around axons of PNS  Derived from neural crest cells

o Sertoli—produce testicular fluid (not testosterone) o Leydig—produce testosterone

o Fibroblast—produces collagen and reticular fibers, most common cell of CT o Osteoblast—forms bone matrix and gives rise to osteocytes

o Sustentacular (supporting) cell—internal ear (organ of Corti), taste buds, olfactory epithelium. They are the taller cells on the basement epithelium.

o Pyramidal—cerebral cortex (cerebrum)

 The pyramids contain upper motor neuron fibers only

o Endothelial—lining blood and lymph vessels, endocardium inner layer o Ependymal—lining brain ventricles and spinal cord

o Ganglionic—in the ganglion of peripheral to CNS

o Globular—transitional epithelium (kidney, ureter, bladder) o Prickle—stratum spinosum of epidermis

o Chromaffin—adrenal medulla and paraganglia of Symp NS o Purkinje—cerebellar cortex (cerebellum)

o Clara—terminal bronchioles

o Goblet cells—mucous MBs of female reproductive tract, respiratory tract, and intestines o Interstitial—CT of ovary and testis

o Islet—pancreas

o Juxtaglomerular—renal corpuscle of kidney o Hepatocyte—liver

- Cell replication: o Chromosomes:

 = DNA + protein (histones)

 Appear as chromatin granules called chromatids, attached to centromeres when replicating o Chromatin:

 A complex of DNA & proteins (the proteins are either histone proteins or non-histone proteins) • Histone proteins:

o (+) charged proteins enriched w/ lysine & arginine o Involved in DNA packaging

• Non-histone proteins:

o Enzymes invovled in nuclear functions such as replication, transcription, & DNA repair

 Is the cell component that is genetically continuous from one generation to the next (not nuclear membrane or golgi complex)

 Loose form of DNA & transcriptionally active o Heterochromatin:

 Highly condensed & transcriptionally inactive

 Almost the entire inactive X chromosome somatic cells in a woman is in this form o Mitosis:

 Splitting of nucleus & cytoplasm→two diploid (daughter) cells w/ identical genetic constitutions

• Keeps the same 2N (diploid) – the Q reads: The diploid number of chromosomes is perpetuated in somatic cells by a process of mitosis

 M phase – mitosis (karyokinesis) division of the nuclear parts of cell (no protein synthesis) • See Below (PMAT)

 Cytokinesis – division of the cytoplasm, accompanies mitosis  Interphase (inactive phase) – period between one mitosis and the next

o G1 phase – 1st growth phase

 By far the most variable cycle period timewise among different types of cells o S phase – when DNA is replicated

o G2 phase – 2nd growth phase  Four active phases:

• Prophase

o Gradual coiling up of chromatin in nucleus

o Individualization of chromosomes, initiation of mitotic spindle w/ centriolar duplication o Phosphorylation of the nuclear lamina during prophase initiates nuclear disassembly • Metaphase

o Disappearance of the nuclear envelope & nucleoli o Chromosomes line up at the equatorial plate o Spindle is complete

• Anaphase

o The chromosomes split longitudinally and migrate to poles o Beginning of cell division

• Telophase

o Nucleolar restitution w/ nuclear envelope formation o End of cell division

o # of chromosomes after telophase???  46?? Only if you’re counting PAIRS BEFORE Cytokinesis • Cytokinesis

o Splitting of the cytoplasm o Occurs right after telophase o NOT essential for Mitosis to occur o Meiosis:

 Gametes – genetic material between homologus chromosomes is intermixed  Two divisions separated by a resting phase

 Total of 4 daughter cells, each w/ ½ the original # of chromosomes  Goes to Haploid

CONNECTIVE TISSUE

Types Description & Function Example

Epithelial tissue May be one or several layers thick; lower surface bound to a supportive basement MB of glycoprotein, mitotically active tissue; line all body surfaces, cavities, and lumina and are adapted

Outer layer of skin, linings of GI tract, urinary bladder, ducts and vessels; alveoli of lungs; and covering of viscera and body CT Proper Highly vascular (except cartilage); contain considerable intercellular

matrix; mitotically active tissue, support or bind other tissues and provide metabolic needs

Tendons and ligaments; cartilage and bone, adipose, blood

Muscle Limited mitotic activity; fibers are adapted to contract in response to stimuli; movement of materials through the body, the movement of one part of the body

Smooth, skeletal, and cardiac muscle

Nervous tissue Limited mitotic activity; respond to impulses to and from all body organs Neurons and neuroglia CONNECTIVE TISSUE

- CT in general:

o Derived from mesenchyme (mesoderm) o Contains more intercellular material than cells o Most common cells are the fibroblasts & macrophages - CT Types:

o Dense CT – provides tendons & ligaments w/ strong, flexible support; has high [fiber]  Dense regular:

• Consists of tightly packed fibers arranged in consistant pattern – EXs include tendons, ligaments, & aponeuroses  Dense irregular:

• Consists of tightly packed fibers arranged in an inconsistent pattern

• Found in dermis, submucosa of the GI tract, fibrous capsules, and deep fascia

o Loose CT – (aka areolar CT) contains large spaces separating the fibers & cells, and contains a lot of intracellular fluid - Collagen Types:

o Type I: most abundant – found in dermis, bone, tendon, dentin, fibrous cartilage, fascias, late wound repair. The #1 (most common) collagen is type I

o Type II: mainly in hyaline & elastic cartilage, vitreous body Type II for 2 eyes – (get it…there are 2 I’s.)

o Type III: major component of reticular fibers (in skin, BVs, uterus, granulation tissue) – think “three on the (BV)” o Type IV: found in basal lamina of basement MBs – think “four on the floor”

o Type V: present in fetal MBs “Type Five to come Alive” o Type X: epiphyseal plate

- Tendons/ligaments:

o Ligament – band of CT (DRCT) that binds bone to bone o Tendon – band of CT (DRCT)that attaches bone to muscle

• More specifically, it secures the muscle fascia to periosteum  Aponeurosis = a sheet-like tendon

o ***When a tendon or ligament attaches to bone, the attaching fibers are called Sharpey’s fibers (it’s not just in teeth)  These are the periosteal collagen fibers that penetrate the bone matrix, binding the periosteum to bone

- Fasciculus

o A bound group of individual muscle fibers

o Fasciculi are the bundles of muscle fibers composing the muscle - Fascia

o Each muscle is surrounded by fascia, which secures the muscle to a tendon o Composed of dense regular CT (DRCT)

- Intercellular Junctions:

o Six major types of cell junctions in humans:  1) Tight junctions (zonula occludens)

• Greatest resistance to substances moving between cells o Think Keep it tight so nothing gets through  2) Intermediate junctions (zonula adherens)

• Belt-like – connects two neighboring cells

 3) Desmosomes (macula adherens) (Think macules are spots – like macula of the eye or melanotic macule.) • Spot-like – connects two neighboring cells

o Tonofibrils (tonofilaments) are found in the desmosome (spinosum???)  4) Hemidesmosomes – intermediate filaments

• Spot-like – connects plasma MB of an epithelial cell to the underlying basal lamina o Epithelium anchored to the basal lamina and thus to the underlying CT

• Common in stratified epithelium of skin and junctional epithelium of the epithelial attachment • Part of the oral cavity which is directly attached to the periosteum??  Hemidesmosomes to the CT • Bullous pemphigoid:

o Involves disruption of hemidesmosomes & consequent separation of the epithelium from the basal lamina  5) Focal contacts

• Spot-like – connects plasma MB of a fibroblast to the surrounding CT

o Points where actin filaments within the cell are attached to the basal lamina.

o These are dynamica and are important in migration of epithelial cells for wound repair.  6) Gap junctions

• Specialized areas of cell MB – connects neighboring cells • Communicating junctions

• Organized collections of protein channels that allow ions/small molecules to passively traverse between connected cells • Separate from components of the junctional complex

• Exist in all multicellular organisms and in almost all cell types

• Some exceptions – skeletal muscle (Because you want recruiting ability), RBCs, & freestanding cells such as circulating lymphocytes

 Miscellaneous

• Adherens jxns – provide strong mechanical attachements bw adjacent cells. They are built from transmembrane proteins Cadherins and Catenins. Catenins are connected to actin filaments.

• Note: One of the oncogenes frequently found with colon CA is mutated version of a protein that usually interacts with catenins. Loss of functioning adherens may  tumor metastasis.

EPITHELIAL TISSUE

- Classified according to cell shape & number/arrangement of cell layers - Functions of Epithelium:

o Protection, absorption, excretion, and secretion - Types of Epithelium:

o Simple squamous epithelium:

 Found where diffusion & filtration occur

 Endothelium lining BVs & mesothelium lining body cavities  Alveoli of the lungs

o Simple cuboidal epithelium:

 Collecting ducts, as well as proximal & distal tubules of the kidney  Thyroid follicles

 Respiratory Bronchioles o Simple columnar epithelium:

 Specialized for secretion or absorption  Lines the majority of the GI system

• Small & large intestine, gallbladder, & stomach (epi associated with the tubular part of the GI tract) • There is a distinct epithelium change between the esophagus and the stomach.

 Uterine epithelium

 Salivary gland striated ducts o Stratified squamous epithelium:

 Usually contains cuboidal cells in the deeper layers & squamous cells in the surface layer  This tissue is well adapted for abrasion and protection – most resistant to trauma

 Broadest classification of epithelium

 Found on skin, linings of mouth, oropharynx, laryngopharynx, esophagus (usually not keratinized), anus, and vagina  When it thickens, rete pegs increase in size, and intercellular bridges become more evident

o Stratified cuboidal epithelium:  Ducts of the sweat glands o Stratified columnar epithelium:

 Large ducts of salivary glands  Male urethra

o Specialized EXs:

 Pseudostratified ciliated columnar epithelium:

• Respiratory Mucous MB of nasal cavity, paranasal sinuses, nasopharynx, trachea, & bronchial tree

o Not the lining of the respiratory bronchioles, which lose their cilia and change to cuboidal and then to squamous

• Parts of the male reproductive tract  Transitional epithelium

• Stratified tissue that lines the urinary bladder, ureter, and upper part of the urethra • Contains dome-shaped superficial cells that change form when contracted or stretched

 When epithelial cells specialize so that a free border is characterized with the presence of microvilli, then the cell possesses either a striated or brush border (not pseudopoda or cilia)

Epithelium Cells Function

Simple Squamous Diffusion and filtration

Cuboidal Secretion, excretion, or absorption

Columnar Absorption, secretion, and protection

Pseudostratified Columnar Secretion and transport of particles out of air passages

Stratified Squamous Protection, prevents water loss

Cuboidal Protection and secretion

Columnar Protection

Special stratified: transitional Varies between cuboidal and squamous Permits expansion - Functions of skin:

o Prevention of body dehydration o Synthesis of Vit D

o Prevention of pathogen entry o Regulation of body temperature - Skin – consists of two principle layers:

 Develops from embryonic ectoderm  Avascular

 Outer cells are dead, keratinized, & cornified

o SIDE BAR: Excessively thickened layer of the straum corneum composed of:

 orthokeratin (hyperorthokeratosis): ↑ keratin layer without residual nuclei (Normal) and uneven surface (so you need ortho)  parakeratin (hyperparakeratosis): ↑ keratin layer with shrunken (pyknotic) residual nuclei (more even surface)

o In denture pt that continually wears them and eroded alveolar bone, the underlying alveolar mucosa is best described as gingival mucosa becoming orthokeratinized mucosa

- Basement MB:

o Thin structure that attaches epithelium to underlying CT in contact w/ the dividing layer of cells

o Consists of glycoprotein from the epithelial cells and a meshwork of collagenous and reticular fibers from the underlying CT o Type IV collagen

o Contains Hemidesmosomes o Consists of:

 Basal lamina – develops from epithelial cells

• Basal epithelial cells are most likely to be in mitosis  Reticular lamina – develops from CT

o Lamina Lucida/Densa??????

o Dermis (inner) – deeper, thicker layer of the skin  Consists of dense irregular CT

 Develops from embryonic mesoderm  Contains

• BVs & lymphatics • 5 types of nerve endings

o (one Q reads: The dermis contains a wider variety of nerve endings than does the epidermis) • Desmosomes

• Mitotic cells  Sebaceous glands

• Associated with hair follicles and derived from ectoderm • Not found on palms of hands/soles of feet

 Sweat/oil glands and hair follicles  Papillary layer of dermis:

• Thin & less fibrous

• Has projections (papillae) that extend up toward the epidermal layer (rete pegs) • Finely constructed, thin, loose CT

• Contains fibroblasts, mast cells, & macrophages • Elastic fibers are abundant and provide the skin tone  Reticular layer of dermis:

• Thick, fibrous, dense irregular CT • Continuous w/ the hypodermis

• Reticular fibers are abundant (Type III)

• Collagenous fibers & elastic fibers are also present • More fibers & fewer cells than in the papillary layer

o Tissue fluid reaches the epithelium in the skin through the ground substance of CT from capillaries - Hypodermis:

o Subcutaneous layer found beneath the dermis that binds skin to underlying structures  Connects dermis w/ underlying fascia of muscle:

o Composed of loose areolar CT, adipose tissue and BVs & and lymphatics  Major site of fat deposition (50% of body fat)

• The Q actually asks: Where is fat found? & the answer is NOT dermis; “submucosa” or “CT layers” are options, which works for the hard palate (submucosa), but maybe not the skin…???

 Good blood supply

- Epidermis: (BG Stars Gives Lots of Charity)

o Outermost portion of skin – develops from embryonic ectoderm o 1) Stratum Basale (= Stratum Germinativum):

 Least cytodifferentiated

 Contains cuboidal or low columnar cells that exhibit lots of mitosis  Contains tonofibrils in the cytoplasm

 Melanocytes are located here

 Forms epithelial root sheath of hair follicle o 2) Stratum Spinosum:

 = prickle cell layer

 Contains cells called Langerhans cells (unknown function – perhaps immune response - APCs)  Malpighian layer denotes the stratum basale and stratum spinosum together

 In the “prickle cell” layer of sulcular epi, the space in between cells is occupied by a small amount of tissue fluid, NOT keratin or capillaries – keratin is intracellular, capillaries don’t reach here.

 THICKEST LAYER??, except for Thick Skin

- The following 3 Layers are NOT present in NON-Keratinized Oral Epithelium o 3) Stratum Granulosum:

 Contain keratohyalin granules in the cytoplasm (not melanin or keratin granules) o 4*) Stratum Lucidum:

 Clear band of cells containing eleidin which is transformed into keratin as this layer becomes part of the stratum corneum  Most prominent in thick skin (palms & soles)

 Absent in the thin skin and (orthokeratinized oral mucosa, which is thin skin) • NOT present in the oral cavity

o 5) Stratum Corneum:

 Composed of closely packed dead cells filled w/ keratin  Thickest stratum corneum is found in the palm

 Aka “horny” layer - Some cells of epithelium

o Keratinocyte:

 Cell type most common in epidermis of skin  Specialized to produce keratin (a protective protein)

 Tonofibrils & desmosomes are especially well developed in keratinocytes o Melanocytes: produce melanin

o Langerhans cells: antigen presenting cells, part of immune system o Merkel cells: associated w/ nerve endings

o Inflammatory cells: lymphocytes, monocytes, neutrophils

- Cutaneous appendages: (see Kaplan in Integument chapter for all the details on these) o Eccrine (merocrine) sweat glands

o Apocrine sweat glands o Sebaceous glands o Hairs

o Nails - Oral epithelium:

o Some structures found in the oral mucous membrane:

 Basal lamina, lamina propria, keratohyaline granules (deeply stained granules in cytoplasm), stratified squamous epithelium o Covered w/ stratified squamous epithelium

 Areas of oral stratified squamous keratinized: gingiva, hard palate (area of mechanical stress) o Permeabilities of oral mucosa:

 Sublingual > buccal > palatal

 Is based on relative thickness & degree of keratinzation

• EX: sublingual mucosa is relatively thin & non-keratizined and thin lamina propia (great for meds) o Sublingual musosa is the thinnest epithelium of the oral cavity

o Oral cavity is highly acceptable for systemic drug delivery  Mucosa is relative permeable w/ a rich blood supply

 Virtual lack of Langerhans cells makes the mucosa tolerant to potential allergens

 Route also bypasses the first-pass-effect & avoids pre-systemic elimination in the GI tract  EX – nitroglycerin tablets given sublingually for rapid absorption

 NOTE: alveolar mucosa is similar to sublingual mucosa – appears red due to the numerous BVs & thin epithelial covering o CT of oral cavity (referred to as lamina propria):

 Forms mechanical support & carries BVs & nerves  Two layers:

• Papillary layer – directly under epithelial layer, more cells, tone • Reticular layer – dense, fibrous layer located under papillary layer

 Oral mucosa of the cheek has a thinner lamina propria then the outer surface of the lip o Submucosa:

 Located between CT and muscle tissue

 Present only in areas requiring a high degree of compressibility & flexibility (cheeks, soft palate)

• Kaplan states that it is defined Submucosa, but immovable because it is tightly bound to underlying periosteum • The Anterior part contains much adipose tissue, and posterior part of the hard palate is full of glands o NOTE: the most outstanding difference between the gingiva and the mucosa of the hard palate is the presence of glands CARTILAGE/BONE

- Cartilage is avascular – heals slowly after injury

- No calcium salts are present – cartilage doesn’t appear on x-rays - Can support great weight, yet it is flexible & somewhat elastic

o Firmness of cartilage depends on:

 Electrostatic bonds between collagen fibers & GAG side chains of matrix glycoproteins  Binding of water to the (-) charged proteoglycan complexes

- Cartilage has a preponderance of amorphous ground substance over fibers

- Chondrogenic cells = undifferentiated mesenchymal cells important to growth & development of cartilage - Chondrocytes:

o Reside in depressions in matrix called Howship’s lacuna. (??I thought Howships lacunae are depressions formed by osteoclasts resorbing bone).

o The only blood supply is provided by BVs entering cartilage through the perichondrium o Secrete a hard, rubbery matrix around themselves

- Three subtypes: o Hyaline

 Most common type

 Matrix contains many, closely packed, fine collagenous fibers

 Has a capsule around the chondrocytes which represents the youngest layer of intercellular substance  Covers & protects bone

 Precursor to bone – in long bones, hyaline provides a region for bone to grow in length  Found where strong support & some flexibility are needed

 Forms nearly all of fetal skeleton

 May grow interstitially, where bone only can grow appositionally  In adults:

• Articular cartilage – smooth and slippery, it lines movable joints • Costal cartilages – at the sternal ends of the ribs

• Respiratory cartilages – movable external nose and septum, larynx, trachea, and the bronchial walls • Auditory cartilages – external auditory meatus and pharyngotympanic tube

 Ground substance of hyaline cartilage is basophilic because it contains sulfated proteoglycans called glycosaminoglycans

• GAGs can readily bind & hold water – allows tissue to assume a gelatinous nature resistant to compression and also permit some degree of diffusion

• Most abundant GAG is hyaluronic acid o Fibrocartilage

 Most closely resembles dense, irregular CT  Matrix contains dense collagenous fibers  Withstands tension & compression

 Found in intervertebral discs (vertebra), knee joint, TMJ, & symphysis pubis o Elastic

 Matrix contains collagenous & elastic fibers

 Similar to hyaline cartilage but the fibers are not as closely packed  More importantly, elastic cartilage contains many elastic fibers (elastin)

 Forms the external ear (pinna) and is also found in the epiglottis, the auditory meatus, & larynx - Tropocollagen

o Protein molecule in BOTH collagen and reticular fibers - Perichondrium:

o Consists of a fibrous outer layer (connective tissue MB) and a chondroblastic inner layer o Very important to cartilage growth

- Cartilage growth:

o Interstitial – chondrocytes divide w/in cartilage – occurs in epiphyseal plates & articular cartilages. Bones lengthen thru interstitial growth (at the cartilaginous epithelial plates – interstitial growth could not occur anywhere but at the plates). o Appositional – where surface perichondrium lays down new layers – results from differentiation of perichondrial cells. Bones

increase in girth thru appositional growth. - Mineralization of Bone

o All of the following are contributors to the mineralization of bone:  Holes or pores in collagen fibers

 Release of matrix vesicles by osteoblasts

 Alkaline phosphatase activity in osteoblasts and matrix vesicles

 Degradation of matrix pyrophosphate to release an inorganic phosphate group – (is this what Alkaline phosphatase is doing?)

 NOT Release of acid phosphatase by osteocytes trapped in lacunae - Bone growth:

o Appositional – below the periosteum is a fibrous outer layer & a cellular inner layer of osteoblasts, which lay down bone  Because of bone’s rigid structure, interstitial growth is NOT possible

o Bone increases in size (width) by way of appositional growth by osteoblasts (Not interstitial) o Do not confuse bone growth w/ bone formation

 Bone forms by either endochondral ossification or intramembranous ossification - Endochondral bone formation: (Think ENDO like long bones (files, etc.)

o Cartilage is precursor for bone in this type of growth

o The epiphyseal plate (disc) is a wedge of hyaline cartilage accounting for this increase  The plate is found between the epiphysis & diaphysis at each end of a bone

 Cartilage cells of the epiphyseal plate form layers of compact bone tissue, adding to the bone length (by interstitial growth in the cartilaginous epiphyseal plate)

 The disc becomes inactive in most individuals by late teens/early 20s

o 1° ossification center – near the middle of the diaphysis. Responsible for formation of diaphysis o 2° ossification center – in the epiphysis; forms later. Responsible for formation of epiphysis.

o Metaphysis – the region between the 1° & 2° ossification centers. Growing zone of cartilage that separates the epiphysis and diaphysis until adulthood.

o The Diaphysis  shaft

o Here are the steps, all concise-like:

 1) chondrocytes proliferate in epiphyseal plate

 2) chondrocytes hypertrophy on diaphyseal side of the area  3) matrix calcifies

 4) chondrocytes die

 5) osteoblasts lay down layer of primary bone along the bone spicules - Zones of the Epiphyseal Plate

o Zone of resting cartilage  Nearest to the epiphysis

 Chondrocytes are disordered and are not dividing rapidly o Zone of Proliferation

 New cartilage is produced by interstitial growth  Multiple chondrocytes stack up forming columns o Zone of Hypertrophy

 Chondrocytes Mature and Enlarge – Lacunae also appear swollen

 More mature ones are at the diaphysis end and less mature are at the epiphysis end o Zone of calcification

 Thin layer of mineralized matrix

 Death of hypertrophied chondrocytes occurs and the lacunae are invaded by blood vessels

 Osteoblasts from the endosteum, travel with the connective tissue of blood vessels and aggregate on the calcified cartilage surfaces

 New bone matrix is deposited by appositional bone growth, then remodeled

o *The width of the epiphyseal plate remains constant because as the bone elongates, there is remodeling inside the metaphysis o Bones fuse between 12 and 25 depending on bone and leave an epiphyseal line

o Plate closes at age 18?? 24?? - Bone Repair

o Bridging callus (A composite mass of tissue that forms at a fracture site to establish continuity between the bone ends; it is composed initially of uncalicifed fibrous tissue and cartilage, and ultimately of bone.)forms

o Periosteal callus forms o New endochondral bone forms

o NOT new osteons grown across the callus

EMBRYOLOGY General Embryology

- Cleavage

o Begins w/in 24 hours of zygote formation

o With each division, the daughter cells (blastomeres) become smaller (no cell growth)

o Compaction – begins w/ the 8-cell stage – blastomeres flatten & are held together by tight junctions o Morula – by day 3 or 4, consists of the 16-32 cells, Solid Mass

 The First solid ball of cells to form in the embryo - Blastocyst formation

o Blastocele

 Fluid begins to accumulate in the intercellular space & forms a central cavity known as the blastocele o Blastocyst

 In what stage do the cells start to have an inner cell mass?  Blastocyst  Is the zygote, now free of its zona pellucida

 Embryoblast – inner cell mass – projects into the cavity – gives rise to the embryo proper • Which cells turn into the inner layer of the fetus?  I think Embryoblast

 Trophoblast – outer cell mass – forms outer epithelial layer – gives rise to the fetal portion of the placenta • Think Troph – i.e. has affinity to travel to uterine wall!

- 1st _{Week: Implantation}

o Begins by the end of the 1st week

o Upon implantation, the trophoblast produces hCG, a hormone that maintains the corpus luteum (which secretes progesterone)

• Excessive growth of the trophoblast results in hydatiform moles (hCG) which can fill the uterus and result in fetal death

• Also, the trophoblast can form the highly malignant chorionepithelioma, a tumor of the chorionic villi

o Ectopic pregnancy – implantation outside the uterus - 2nd _{Week: Bilaminar disc}

o Epiblast – primary ectoderm – High columnar cells, during 3rd _{week  forms ectoderm and mesoderm}  form the amniotic cavity – On top

o Hypoblast – primary endoderm – Low cuboidal cells  contributes to primary yolk sac (or remaining

Blastocyst) – On the bottom - 3rd _{Week: Trilaminar disc}

o Primitive streak

 Linear thickening of the ectoderm cells  Defines the cephalocaudal axis of the embryo  Delimited rostrally by the primitive node

o Epiblast cells invaginate between epiblast & hypoblast – forms the intraembryonic mesoderm o Notochord formation: (Get your Honda acCORD on your 16th birth day)

 Day 16 – cells of the primitive streak migrate rostrally & form the tube-like notochordal process  The notochord is a rod-shaped body found in embryos of all vertebrates

 Composed of cells derived from mesoderm and defines the primitive axis of the embryo  Found on the ventral surface of the neural tube

 The notochord induces the the thickening of the ectoderm to form the neural plate  Turns in to the Nucleus Propulsus

o Neural plate begins to form

o Buccopharyngeal Membrane Ruptures

- What causes the infolding of the “head thing” in embryology?

o Neural cells growing OR branchial arch formation?? –I’m 100% sure its form neural cells growing! - 4th _{– 8}th _{Weeks: Embryonic Period}

o Week 4 –

 For the 4 chambers of the heart begins to beat; upper/lower limb buds begin to form for the 4 limbs, and 4 Visible Branchial Arches

 Neural Plate

• The neural plate increases in length as the primitive knot and primitive streak move caudally • Invagination of the neural plate at day 18 forms the neural groove

• The edge of each fold is known as the neural crest

• Neural tube is formed when the crests fuse, starting at the 4th somite region (neck) and proceeding in cephalic and caudal directions

• The cephalic end of the neural tube will eventually dilate to form the forebrain, midbrain, and hindbrain o The spinal cord is formed from the remainder of the neural tube

 Nueral crest cells (Ectomesenchyme)

• Form Posterior root ganglia, sensory ganglia of the cranial nerves, autonomic ganglia, meninges, Schwann cells, suprarenal cells, and Melanocytes

 Head and Tail Folds

• The entoderm (endo) germ layer gives rise to the GI and depends on BOTH the cephalocaudal folding and the lateral folding of the embryonic disc in a tubelike fashion

• HEAD FOLD

• Rapid longitudinal growth of the CNS causes the cephalic and caudal ends to bend and form head and tail folds o As a result the brain comes to lie cranial to the cardiogenic area and septum transversum, which contributes to the

formation of the diaphragm.

o Part of the yolk sac becomes incorporated into the embryo as the foregut

 This cavity opens into the midgut via the anterior intestinal portal and is bounded anteriorly by the prochordal plate, which is known at this stage as the buccopharyngeal membrane

• This membrane forms the back of the stomodeum and ruptures at the end of the 3rd week to establish communication between the amniotic cavity and the primitive gut

• TAIL FOLD o Blah, blah  Lateral Folds

• The continued growth of the somites causes the expanding lateral margins of the embryonic disc to bend ventrally, forming lateral folds

o As a result, part of the yolk sac is taken into the embryo to form the midgut

o In addition, this folding constricts the initially wide communication between embryo and yolk sac to a narrow, long vitelline duct, which eventually lies w/in the umbilical cord

 What causes the infolding of the “head thing” in embryology?

• Neural cells growing OR branchial arch formation?? –I’m 100% sure its form neural cells growing! • THIS is why I think the answer to the above yellow question is neural cells growth

o 3rd-8th _{week – fetus most susceptible to teratogens} o Ectodermal derivatives:

 Surface ectoderm

• Otic placode & lens placode • Epidermis

• Hair & nails

• Subcutaneous glands • Enamel

• Anterior pituitary gland • Mammary glands

• Hair, enamel, sweat glands & salivary glands are all derived from ectoderm (dentin is not)  Neuroectoderm:

• Posterior pituitary gland • CNS neurons

• Oligodendrocytes & astrocytes • Pineal gland

 Neural crest:

• ANS (e.g., autonomic ganglia) • Sensory ganglia of CNs • DRGs

• Meninges • Schwann cells

• Adrenal medulla (chromaffin cells) • Melanocytes

• Odontoblasts

o Mesenchymal (mesodermal) derivatives:  CT (bone, cartilage)

 Muscle  Dermis

 Urogenital system  Adrenal cortex  Spleen

 Serous MBs lining the pericardial, pleural & peritoneal cavities o Endodermal derivatives:  GI system  Thyroid/parathyroids  Thymus  Lungs  Liver  Pancreas

 Lining of respiratory tract, bladder & urethra - 10th _Week:

o Genitalia have M/F characteristics Head & Neck Embryology

- Stomodeum = stomatodeum:

o Slight depression on the surface ectoderm o Represents the primitive oral cavity

o Separated from primitive pharynx by buccopharyngeal MB (oropharyngeal MB)  Composed of ectoderm externally & endoderm internally (no mesoderm)  Covers the stomatodeum

 Ruptures at 3 ½ weeks (forming max palatal shelves) o Prochordal Plate

 Consists of the endoderm of the roof of the yolk sac and embryonic ectoderm  Does NOT contain mesoderm

- Branchial Arches = pharyngeal visceral arches o General features:

 A series of rounded mesodermal ridges on each side of head & neck of embryo at 4 weeks

• Develop in the 4th week as neural crest cells that proliferate & migrate into the future head & neck region • By end of the 4th week, FOUR well-defined pairs of branchial arches are visible externally

o The 5th & 6th are small & cannot be seen on the embryo surface

 Each branchial arch contains a cartilaginous bar or rod, a muscular component, an artery, & a nerve  1st_-3rd _{arch play role in formation of face & oral cavity}

• 1st arch develops into Mn & large part of Mx • 1st, 2nd & 3rd arches play role in tongue development  Contain striated muscle, not from somites

 Branchial arches (are SVE – special because they are striated, but not developed from body wall or somites)

o From the above picture, the facial process indicated w/ the letter A gives rise to the secondary palate o Cartilages of each arch:

 1st arch cartilage (M: Meckel’s, Mandible, Malleus, Muscles of Mastication, Mylohyoid) • 1st arch develops into Mn & large part of Mx

• A model for the Mn – but does not form any part of Mn

o Fate is dissolution with minor contribution to ossification o Mandible forms before the maxilla.

o Both mandible (except for condyles) and maxilla are mostly formed by intramembranous ossification. • Closely related to development of the middle ear

o Ossifies to form the malleus & incus

• All 8 muscles innervated by V3 (4 mastication, 2 tensors, anterior belly of digastric, and mylohyoid)

• NOTE: CN V supplies the muscles derived from the 1st pair of branchial arches  2nd _{arch cartilage (Reichert’s)}

• Closely related to development of the middle ear o Ossifies to form the Stapes (Second Stapes)

• Think S  Second, Stapes, Styloid Process, Stylohyoid, Seven (VII) • Forms part of the hyoid bone

• Also forms Styloid process of the temporal bone • Also forms the stylohyoid ligament

• Stylohyoid muscle is from the 2nd arch

• All facial expression muscles innervated by CN VII  3rd _{arch cartilage}

• Ossifies to form part of the hyoid bone • Stylopharyngeus muscle

• Derivatives of the 3rd arch are innervated by CN IX

• Think Pharynx: stylopharyngeus & glosspharyngeal nerve  4th _{& 6}th _{arch cartilages:}

• Fuse to form laryngeal cartilages (except for the epiglottis) • All other pharyngeal and laryngeal muscles

• XI via X:

o Spinal part of XI

 Goes to SCM and trapezius o Cranial part of XI

 Joins X

 Goes to pharyngeal muscles from vagal branches  Goes to laryngeal muscles via recurrent laryngeal

 NOTE: CN XII provides GSE fibers derived from the Occipital somites, not any arches • 4th arch:

o Most pharyngeal constrictors, Except Cricopharyngeus

o THE EXCEPTION  Cricothyroid – which you would think is the area of 6th arch o Levator veli palatini

o Innervated by superior laryngeal branch of CN X • 6th arch:

o All intrinsic laryngeal muscles (except cricothyroid) – superior laryngeal branch of X o The EXCEPTION  Cricopharyngeus – which you would think is the area of 4th arch o Innervated by recurrent laryngeal branch of CN X

 5th _arch

• Absent (short-lived or not developed)

o A little more about the arches: (yup, I know, I suck & you’re pissed) o 1st Arch:

 Divides at 4 weeks embryonic development to form Mn & Mx processes

• Mn (except condyles) & Mx are mostly formed by intramembranous ossification  Develops into two prominences or processes:

• 1) Mn process (larger) – forms the Mn & lower lip

o Mn forms by merging of medial ends of Mn processes during the 4th week (Mn forms before Mx)

• 2) Mx process (smaller) – forms the Mx, zygomatic bone, squamous part of the temporal bone, most of upper lip o Mx forms by merging of Mx processes

o The upper lip is formed from the Mx processes and medial nasal processes

o The medial nasal process form the center of the nose and lateral nasal processes form the ala of the nose o Maxillary teeth are developed from Arch I and a globular process

o NOTE: the intermaxillary arch is NOT a derivative of the 1st Arch o The palatine shelf is a medial extension of the Mx process

o Lateral palatine processes of Mx process – secondary palate (hard and soft palate)

o Primary Palate is formed by the medial nasal processes and join the secondary palate at the jxn of the nasopalatine canal

 May be unilateral or bilateral

o ***Cleft palate – failure of fusion of the lateral palatine processes, nasal septum &/or median palatine process  Most common in Asians

 Corners of the mouth

• Formed by fusion of Mx & Mn processes  Tuberculum impar: (median tongue bud)

• Median, triangular elevation which appears in the floor of pharynx just rostral to foramen cecum • Forms from 1st branchial arch

• Gives first indication of tongue development in embryo at 4 weeks  Lateral lingual swellings (two distal tongue buds):

• Develop on each side of median tongue bud

• Elevations are the result of proliferation of mesenchyme of 1st arch • Swellings fuse to form the anterior 2/3 of tongue (mucosa and all)

o Delineated by circumvallate papilla??  Bifid tongue:

• Results from lack of fusion of distal tongue buds (or lateral swellings) • Common in South American infants

o 2nd Arch:

 Copula (helps to form posterior 1/3rd₎ o 3rd Arch:

 Posterior 1/3 of tongue is formed by two elevations: the copula (2nd _{arch) & the hypobranchial eminence (3}rd _arch) - SIDE BAR:

o Bifid uvula:

 Results from failure of complete fusion of palatine shelves - Pharyngeal pouches: (NOT ARCHES)

o Paired evaginations of pharyngeal endoderm lining the inner aspects of the branchial arches in the neck region  NOTE: the parotid gland is NOT a derivative of a pharyngeal pouch

 Messed up development of 3rd _{& 4}th _{pouches→DiGeorge syndrome→leads to T-cell deficiency & hypocalcemia}

Pharyngeal Pouch Structures Derived

1st _{Tympanic MB, audtitory tube, and middle ear cavity, mastoid air cells} 2nd _{Lymphatic nodules and palatine tonsils}

3rd _{Inferior parathyroid gland, thymus gland (Hassall’s Corpuscles)}

4th _{Superior parathyroid gland, ultimobranchial body which gives rise to parafollicular cells (C cells)} of the thyroid gland (produce calcitonin)

5th Rudimentary structure, becomes part of the fourth pouch - Vestibular lamina

o Separates lips & cheeks externally & the jaw structures internally in the developing embryo o Outer lamina of the 2 epithelial lamina in embryo that separate the palate from the lip!!!!! - Frontal nasal process (prominence):

o Produced by the growth of the forebrain o Develops the forehead and nose - Nasal placodes

o Thickened areas of specialized ectoderm that form on each side of the frontal nasal process o Elevations form at the margin of these placodes

o What makes up the nose?  Medial and lateral nasal processes  Two lateral nasal processes form the sides (alae) of the nose

 Two medial nasal processes form the bridge of nose, nostrils, philtrum (upper lip), & primary palate (anterior to incisive foramen)

o Philtrum

 What forms the philtrum?  Medial Nasal Processes with Maxillary processes - Lips:

o Derived from Mn, Mx, & Medial Nasal processes - Tongue:

o Derived from 1st, 2nd_{, and 3}rd _{branchial arches}  Anterior 2/3

• 1st Arch

• Ectoderm (Mucosa) • Tuberculum impar

• Lateral Lingual Swellings – primary developmental source of mucosa of the anterior 2/3 of the tongue  Posterior 1/3 • 2nd and 3rd Arch • Endoderm • Copula (2nd) • Hypobranchial eminence (3rd)  Tongue NOT formed from macula o At the jxn of the body and root of the tongue is:

 Foramen Cecum

• Lies at the base of the V of the sulcus terminalis  Sulcus Terminalis

• V-shaped demarcation that separates anterior 2/3 from posterior 1/3  Circumvallate Papilla

 NOT Lingual raphe

 Remnant of thyroglossal duct. o Taste in tongue:

 All innervation is from the solitary nucleus  Anterior 2/3: CN VII

 Posterior 1/3: CN IX

 Extreme posterior and soft palate: CN X

ENDOCRINE SYSTEM - Exocrine glands – classified according to:

o 1) Type of secretion:

 Mucous (water & mucin)—buccal glands, glands of esophagus, cardiac & pyloric glands of stomach  Serous (enzymes)—parotid, von Ebner’s glands (Serous ONLY), pancreas & uterine glands

 Mixed—submand. & sublingual glands, glands of nasal cavity, paranasal sinuses, nasopharynx, larynx, trachea, and bronchi o 2) Mode of secretion:

 Merocrine—only the cell secretory product is released from MB-bound secretory granules – EX: pancreatic acinar cells  Apocrine—secretion of product plus small portion of cytoplasm – EX: fat droplet secretion by mammary gland  Holocrine—entire cell w/ secretory product – EX: sebaceous glands of skin & nose (Think Hol = Whole) o 3) Structure of duct system:

 Unbranched—“simple glands” – EX: sweat glands  Branched—“compound glands” – EX: pancreas o 4) Shape of secretory unit:

 Tubular—cylindrical lumen surrounded by secretory cells – EX: sweat glands

 Acinar (alveolar)—dilated sac-like secretory unit – EX: sebaceous & mammary glands

 Tubuloacinar (tubuloalveolar)—intermediate in shape or has tubular & alveolar secretory units – EX: major salivary glands o NOTE: Salivary, sweat, sebaceous, and von Ebner's glands are all exocrine glands

- Pituitary Gland (hypophysis cerebri):

o Master endocrine gland because it controls many other glands through release of tropic hormones  Tropic hormones = hormones that effect the activity of another endocrine gland

o Origin:

 1) Upgrowth from ectoderm of the stomodeum – roof of mouth (anterior pituitary, glandular portion from oral ectoderm) • Rathke’s pouch – diverticulum developing at 3 wks from the roof of stomodeum (primitive mouth) – grows

toward brain

o The anterior lobe of the hypophysis develops from Rathke’s pouch

 2) Downgrowth from the neuroectoderm of diencephalon—floor of brain (posterior pituitary, nervous portion) o Positioned in the sella turcica of the sphenoid bone directly above the sphenoid sinuses

o Structure:

 Adenohypophysis = Anterior Pituitary

• Pars tuberalis, pars distalis, and pars intermedia

• Pars intermedia is an avascular zone lying between the lobes but is considered part of anterior pituitary • Pars intermedia & tuberalis have no proven function in mammals

• NO innervation

• Contains alpha & beta cells

• Hypothalamic-hypophyseal portal blood system – controls rls of

anterior pituitary

 Neurohypophysis = Posterior Pituitary

• Pituicytes  Primary cell of posterior pituitary, fusiform cell closely related to neuroglia • Median eminence, infundibulum and pars nervosa

o The infundibular stalk contains the hypothalamic-hypophyseal tract, which carries axons to the posterior pituitary • Consists mainly of unmyelinated nerve fibers!!!

o Blood supply

 From right & left superior and inferior hypophyseal arteries

 Sinusoidal blood arrangement (sinusoidal arrangement of BVs also found in Liver and Spleen)  Forms a rich vascular portal system

• Portal has two capillary beds • ***Three portal systems in the body:

o 1) Hepatic portal system – 1st capillary bed in intestines & 2nd in the sinusoids of liver o 2) Renal portal system – 1st capillary bed in glomerulus & ????

o 3) Hypothalamus-Hypophyseal portal system – 1st bed in HTh & 2nd _{in Anterior Pituitary}

 Carries the Releasing Hormones produced in the hypothalamus to the anterior pit and have them release further hormones

o Synthesized peptide hormones:

 Anterior Pituitary = pars distalis: FLAT PeG

• The following tissues would be affected if the anterior lobe of the hypophysis were destroyed:

o Thyroid epithelium, zona fasciculata of adrenal gland, interstitial cells of testis, spermatogenic epithelium of testis  NOT adrenal medulla

• Hormones released from:

o Alpha cells – GH & Prolactin (regular hormones) – Alpha for acidic or Eosionophilic pEg o Beta cells – FSH, LH, ACTH, TSH (all tropic hormones)

• Sidenote: The hypophysis is characterized by an anterior lobe w/ alpha & beta cells • Follicle stimulating hormone (FSH):

o Development of graafian follicles & estrogens in the ovary

o Promotes spermatogenesis in males – acts on sertoli cells to produce inhibin and androgen binding protein • Luteinizing hormone (LH):

o Stimulates formation of corpus luteum & progesterone secretion o Stimulates interstitial cells (Leydig cells) of testes to secrete testosterone • Corticotropin (ACTH):

o Controls secretion of adrenocortical hormones (glucocorticoids), which affect glucose, protein, & fat metabolism • Thyroid stimulating hormone (TSH):

o Controls secretion of thyroxine by thyroid, uptake of iodine, and synthesis • **Melanin Stimulating Hormone (MSH) and Beta-Lipotropin

o Secreted from the pars intermedia • Prolactin (Lactotropin):

 The mammary glands are under direct control from the hypophysis o Triggered by rising estrogen levels

• Growth hormone (GH) – aka ‘somatotropin’:

o Growth in general; particularly skeletal system by stimulating aa uptake, protein synthesis, & CHO/fat breakdown o Most plentiful of AP hormones

o Fusion of long bone epiphyses determines if excess GH will result in gigantism (children) or acromegaly (adults) o Produced by acidophils in the anterior pituitary

 Posterior Pituitary – Neurohypophysis or pars nervosa: • Consists of unmyelinated nerve fibers

• Consists of 100,000 axons of the supraoptic and paraventricular nuclei of hypothalamus • Secretes ADH & oxytocin

• Hormones are synthesized in hypothalamus & transported in axons to the poster lobe for storage and secretion o Transport occurs via hypothalamo-hypophyseal tract

• Antidiuretic hormone (ADH) – aka ‘vasopressin’: o Controls rate of water excretion into urine • Oxytocin:

o Helps to deliver milk from glands in breasts to nipples during nursing - Thyroid gland:

o H-shaped structure – two parts joined by a thin isthmus

 The isthmus runs in front of the trachea and contacts it posteriorly o It has rings of epithelial cells surrounding a space filled with colloid

o Characterized by the fact that it functions as the controller of general body metabolism o In adults, the site of origin is seen as the foramen cecum

o Blood supply –

 superior thyroid artery from external carotid, then branches to form the superior laryngeal and enters the thyrohyoid membrane along with the internal branch of the superior laryngeal nerve from the vagus,)

 inferior thyroid artery from thyrocervical trunk)

 SIDENOTE: Vagus, has both the superior laryngeal nerve and the recurrent laryngeal nerve (BOTH do sensory and muscle)

• Pharyngeal branch  Innervates the pharyngeal constrictors except the Cricopharyngeus (VI arch)  THINK Cricos are the ODD balls

• Recurrent Laryngeal  Sensory/PS: Everything from the folds down

 MOTOR: All the motors of the Larynx except Cricothyroid (IV arch) • Superior Laryngeal  Sensory/PS: (Internal branch) above the folds

 MOTOR: (External branch) to the Cricothyroid o Nerve supply – glandular branches of cervical ganglia of sympathetic trunk o Cell types:

 Follicle cells:

• Synthesize thryoglubulin (from tyrosine), which is stored in colloid of each follicle, and is a precursor to T3 & T4 • When pituitary gland secretes thyrotropin, the colloid becomes active & thyroglobulin molecules are released and taken

back into the follicular cells where they become T3 & T4

• Remain inactive at times of low thyroid homrone need – can be activated when necessary for mobilization of colloid found in thryroid

• Colloid in the usual thyroid follicle stains acidophilic (PINK) • Metabolically active follicular colloid stains BASOPHILIC  Parafollicular cells: (C cells)

• Produce calcitonin – lowers calcium & phosphate levels in blood

 Thyroglossal duct – a narrow canal connecting the thyroid gland to the tongue during development • Disappears but persists as the foramen cecum

 An upward extension of the thyroid gland could be a remnant of the thyroglossal duct, a pyramidal lobe, or a muscular slip  Cervical cysts in the midline of the neck is from Thyroglossal duct

- Parathyroid gland:

o Four glands – two superior (superior thyroid artery from external carotid) and two inferior (inferior thyroid artery from thryocervical trunk) pairs of glands on posterior (dorsum) of thyroid gland

o Develops from 3rd & 4th _{pharyngeal pouches}

o Blood supply is mostly from inferior thyroid artery (with contribution from the superior thyroid artery to the superior glands only)

o Controlled by blood levels of calicum – NOT TSH o Cell types:

 Principal cells (chief cells) – secrete PTH, have clear cytoplasm

 Oxyphil cells (acid secreting cells) – granules in cytoplasm, unknown function o PTH:

 Regulates calcium & phosphate metabolism  It is ESSENTIAL for LIFE

 Innervention by superior cervical ganglion (sympathetic)  Low PTH leads to tetany & muscle weakness duel to lack of Ca2+ - Pineal gland:

o Located in the epithalamus of brain and releases the hormone melatonin

o Thought to play role in regulation of sleep-wake cycle, body temperature regulation, and appetite - Adrenal gland:

o Aka ‘suprarenal gland’

o Embedded in adipose tissue above kidneys o Adrenal Medulla:

 Secretes Epi and Norepi

 Secretion of Adrenal medulla is NOT ESSENTIAL FOR LIFE (unlike those of Parathyroids, Adrenal cortex, Anterior pituitary, Pancreatic islets (Langerhans)

 From neuroectoderm (neural crest cells which differentiate into medullary cells called chromaffin cells) • Same embryologic origin as sympathetic ganglia

• So, chromaffin cells of adrenal medulla secrete catecholamine

• So, the adrenal medulla is an endocrine gland of ectodermal origin in the abdomen  Is composed of many cells containing MB-bound osmiophilic granules

 Has an intrinsic stroma consisting primarily of reticular fibers  NOT separated from the cortex by a capsule of collagen fibers o Adrenal Cortex:

 Outside to In: Zona Glomerulosa→Zona Fasiculata→Zona Reticularis (GFR – like Glomerular Filtration Rate) • Also outside→in: Salt→Sugar→Sex (aldosterone→glucocorticoids→androgens)  life gets sweeter  Each Zone of the cortex has endocrine cells:

• Zona Glomerulosa

o Thin layer, clusters of cells beneath CT capsule o Secretes mineralocorticoids, primarily aldosterone • Zona Fasiculata

o Thick middle layer, cells arranged in parallel columns that run at right angles to surface

o Secretes glucocorticoids, primarily cortisol; also small amounts of estrogenic & androgenic-like substances • Zona Reticularis

o Inner layer, cells arranged in interconnecting cords

o Secretes small amounts of cortisol & Dehydoropiandrosterone (DHEA)  Derived from the mesoderm

- Hormones that are ESSENTIAL FOR LIFE: parathyroid, adrenal cortex, anterior pituitary, pancreatic islets (Langerhans) - Thymus:

o Major gland of immune system

o Two soft, pinkish-gray lobes lying in a bib-like fashion below the thyroid gland and above the heart  Encapsulated

o From 3rd branchial pouch

o Primary lymphoid organ (just like spleen, tonsils, lymph nodes, & Peyer’s Patches) o Site of T-cell maturation

o Outer cortex – contains primarily lymphocytes

o Inner medulla – contains T-lymphocytes & Hassall’s corpuscles (thought to be vestiges of epithelium – unknown function)  Are Mature in the Medulla

o The thymus is the immune system organ most isolated from blood

o Master organ in immunogenesis in the young – some believe it monitors total lymphoid system throughout life o Requires zinc – most critical – involved in all aspects of immunity: Vit B6, Vit C, carbonic anhydrase, & others

o No afferent lymphatics of lymphatic nodules – it makes mature T-cells, it doesn’t collect them, so it only needs blood supply. o Blood from the internal thoracic & inferior thyroid arteries

o Innervated by vagus & phrenic nerves o Has double embryologic origin:

 Lymphocytes derived from hematopoietic stem cells (mesenchyme)

 Hassall’s corpuscles (epithelium) derived from endoderm of 3rd pharyngeal pouch o Produces thymopoietin & thymosin

 Both are thymic lymphopoeitic factors – confer immunological competence on thymus-dependent cells & induce lymphopoiesis

 Also produces thymic humoral factor (THF) & thymic factor (TF)

• Important in normal development of immune system→proliferation & maturation of T lymphocytes - Pancreas: