Chapter 5 The Skeletal System Appendicular Skeleton

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Chapter 5 The Skeletal System Appendicular Skeleton

Be Able To

• Identify the bones of the shoulder and pelvic girdles and their attached limbs.

• Describe important differences

between a male and female pelvis.

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Appendicular Skeleton

Introduction

• Bones of the limbs and their girdles comprise the

appendicular skeleton.

• It is composed of 126 bones.

• The pectoral girdles attach the upper limbs to the trunk.

• The pelvic girdles secure the lower limbs.

• Each limb is composed of three major segments connected

together by movable joints.

• The appendicular skeleton enables our movements.

Pectoral girdle

Pelvic girdle

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The Pectoral (shoulder) Girdle

• Each shoulder girdle consists of two bones: the anterior clavicle and posterior scapula.

• The medial end of each clavicle joins the sternum and the distal ends meet the scapulae laterally.

• The scapulae are attached to the thorax and the vertebral column by muscles.

• The pectoral girdles are very light and allow a degree of flexibility and mobility not seen in other parts of the body, due to:

1) The scapula is able to move freely across the thorax, since it is not

directly attached to the axial skeleton.

2) The socket of the shoulder joint is shallow and is poorly reinforced (problem is dislocation).

scapula clavicle

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The Pectoral (shoulder) Girdle: the clavicle

• The clavicle or collar bone is a slender curved long bone.

• Its medial end or sternal end is coned shaped where it attaches to the

manubrium.

• Its lateral or acromial end is flattened where it attaches to the scapula.

• The clavicles brace the limbs by

holding them laterally away form the superior thorax.

• They transmit compression forces from the upper limbs to the axial skeleton.

• They are exceptionally sensitive to muscle pull and will become larger and stronger during manual labor.

clavicle

How is a fractured clavicle treated?

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The Pectoral (shoulder) Girdle: the scapulae

• The scapulae or shoulder blades are thin triangular flat bones.

• Lies on the dorsal surface of the rib cage, between ribs 2-7.

• Each scapula has a superior, medial or vertebral, and lateral or axillary border.

• The axillary border has a shallow fossa called the glenoid cavity, which articulates with humerus of the arm.

• The anterior surface is featureless.

• The posterior surface bears a spine that end laterally in a projection called the acromion

process that articulates with the acromial end of the clavicle at the acromiocalvicular joint.

• The superior border bears the coracoid process that helps anchor the biceps muscle of the arm.

• At the medial end of the coracoid process is the suprascapular notch which serves as a nerve passageway.

Glenoid cavity

Acromion process

Coracoid process

Posterior view

spine

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The Upper Limbs: the Arm

• The humerus is the sole bone of the arm.

• It articulates with the scapula at its

proximal end and with the radius and ulna at its distal end.

• The proximal smooth end or the head fits into the glenoid cavity.

• The lateral greater tubercle and the medial lesser tubercle are sites of muscle attachment.

• The intertubercular groove that separates the tubercles and guides a

tendon of the biceps muscle of the arm to its attachment at the glenoid cavity.

• The deltoid muscle attaches to the deltoid tuberosity.

• The trochlea and capitulum are

condyles that articulate with the ulna and the radius, respectively.

• Superior to the trochlea on the anterior surface is the coronoid fossa.

• On the posterior surface is the olecranon fossa.

Greater tubercle

Lesser tubercle

Intertubercular groove

trochlea capitulum

Coronoid fossa

Medial condyle Lateral

condyle

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The Upper Limbs: the ulna

• The ulna and radius comprise the bones of the forearm.

• The ulna is slightly longer and forms the elbow joint with the humerus.

• The olecranon and coronoid processes are separated by a concave trochlear

notch (articulates with olecranon fossa).

• When the arm is fully extended the

olecranon process locks in the olecranon fossa.

• Lateral to the coronoid process is the radial notch which articulates with the head of the radius.

• The styloid process is narrow and is

connected to the wrist through a ligament.

• The distal ulnar head is separated from the bones of the wrist by a disc of

fibrocartilage.

Olecranon process

Trochlear notch

Coronoid process

Styloid process Head of ulna

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The Upper Limbs: the radius

• The radius is thin at its proximal end and widens distally.

• The head of the radius is shaped like the head of a nail, except that it is

concave.

• The head articulates with the capitulum of the humerus an

articulates with the radial notch of the ulna.

• The radial tuberosity anchors the biceps muscle of the arm.

• The styloid process is an anchoring site for ligaments of the wrist.

• When the radius moves so does the hand.

head Radial tuberosity

Styloid process

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The Upper Limbs: the hand

• The skeleton of the hand includes the bones of the carpus (wrist), metacarpus (palm), and the phalanges (fingers).

• The carpus consists of 8 short bones arranged in 2 irregular rows of 4 bones each that are closely united by ligaments.

• Five metacarpal bones radiate from the wrist to form the palm of the hand.

• These small long bones are not named but are numbered from thumb to little finger 1 to 5.

• The phalanges or digits are numbered 1 to 5 beginning with the thumb or pollex.

• Each hand contains 14 miniature long bones identified by distal, middle, and proximal (thumb has no middle phalanx).

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Chapter 5 The Skeletal System Appendicular Skeleton

Be Able To

• Identify the bones of the pelvic girdle and its attached limbs.

• Describe important differences

between a male and female pelvis.

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Bones of the Pelvic Girdle

• The pelvic girdle is comprised of two coxal bones or hip bones.

• The pelvis is comprised of the sacrum, coccyx, and coxal bones.

• The pelvic girdle attaches the lower limbs to the axial skeleton, transmits weight of the upper body to the lower limbs, and supports the visceral organs of the pelvis.

• Its sockets are deep and are heavily reinforced with ligaments.

• Each coxal bone or os coxae consists of three separate bones during childhood: the ilium, ischium, and pubis.

• The acetabulum on the lateral surface of the pelvis is a deep socket that articulates with the femur.

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The Coxal Bone: the ilium

• The ilium forms the majority of the coxal bone.

• It consists of a body and a

superior wing-like portion called the alae.

• The superior edge of each alae is the iliac crest.

• Each iliac crest terminates at the anterior and posterior iliac

spine which are superior to two small spines, all of which serve as muscle attachment sites.

• The ilium fuses with the sacrum at the sacroiliac joint, where the weight of the body is transmitted from spine to pelvis.

Ala

Anterior superior iliac spine

Anterior inferior iliac spine

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The Coxal Bone: the ischium

• The ischium or “sit down bone”

forms the most inferior part of the coxal bone.

• It is comprised of a thick body and a thinner inferior ramus.

• The ischial tuberosity is thickened inferior surface that bears the

weight of the body when sitting.

• An ischial spine, just superior to the tuberosity, serves as a point of attachment for a ligament from the sacrum.

• The greater sciatic notch allows blood vessels and the sciatic nerve to pass from the pelvis to the thigh.

Ischium

Ischial spine

Ischial tuberosity

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The Coxal Bone: the pubis

• The pubis or pubic bone forms the anterior portion of the coxal bone.

• The bladder rests upon it.

• Superior and inferior rami fuse at the body and

surround the obturator foramen.

• The bodies of each pubic bone are joined by a

cartilaginous disc forming the pubic symphysis joint.

• The pubic arch is inferior to this joint.

Pubis

Obturator foramen

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The Coxal Bone: male and female pelves

• The female pelvis reflects

modifications for childbearing:

wider, shallower, lighter, and rounder.

• The female pelvis must be large

enough to allow the infant’s head to exit at birth.

• The false pelvis is a superior region above the pubic rim that helps support the abdomen and does not restrict childbirth.

• The true pelvis is the region

inferior to the pelvic rim that forms a deep bowl containing the pelvic organs.

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The Lower Limbs

• The lower limbs carry the entire weight of the erect body and are subjected to tremendous forces when we jump or run.

• The more massive bones of the lower limbs are

specialized for stability and weight bearing.

• The three segments of each lower limb are the thigh, leg, and foot.

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The Lower Limbs: the femur

• The femur is the largest, longest, and strongest bone of the body.

• Stress on the femur can reach 280kg/cm².

• The femur articulates proximally with the coxal bone and continues medially to the lower leg.

• The head of the femur has a small pit called the fovea capitis that secures the femur to the hip via a ligament.

• Inferior to the head is the neck, which is the weakest point.

• The lateral greater trochanter and medial lesser trochanter and the gluteal tuberosity serve as muscle attachment sites.

• Distally the lateral and medial condyles articulate with the tibia.

• Anteriorly on the distal femur is the patellar surface for the patella or kneecap.

Greater trochanter

Lesser trochanter Fovea

capitis

Lateral condyle

Medial condyle

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The Lower Limbs: the tibia

• The tibia receives the weight of the

body from the femur and transmits it to the foot.

• At the proximal end lie the concave

medial and lateral condyles which are separated by the intercondylar

eminence,

• The tibial condyles articulate with the corresponding condyles of the femur.

• Inferior to the condyles is the tibial tuberosity that serves as a muscle attachment site.

• The anterior crest and the medial surface are not covered by muscles.

• The medial malleolus is an inferior projection to the distal end of the tibia.

Anterior crest

Medial condyle

Lateral condyle

Medial malleolus

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The Lower Limbs: the fibula

• The fibula is a sticklike bone with slightly expanded ends.

• It articulates proximally and distally with its lateral

aspects of the tibia.

• The superior end is the head and the inferior end is the

lateral malleolus, which

forms the lateral ankle bulge.

• It does not bear weight.

Head

Lateral Malleolus

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The Foot: tarsus, metatarsus, and the phalanges

• Includes the bones of the tarsus, metatarsus, and the phalanges.

• It supports our body weight and acts as a lever to propel the body forward when we walk or run.

• The tarsus is made of several bones that form the posterior half of the foot.

• The talus and calcaneus bear most of the weight.

• The achilles tendon attaches to the calcaneus.

• The cuboid and cuneiform bones articulate with the metatarsals.

• The metatarsals are numbered 1 through 5 starting on the big toe side.

• The enlarged head of the first metatarsal forms the ball of the foot.

• The arrangement of the 14 bones of the toes are arranged in the same manner as the

bones of the fingers.

• The great toe or hallux has only two bones, whereas the rest have three bones each.

phalanges

metatarsals

calcaneus talus

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Chapter 5 The Skeletal System Appendicular Skeleton

Be Able To

• Name the three major categories of joints and compare the amount of movement allowed by each.

• Identify some of the causes of joint

problems.

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Joints

• Joints or articulations have two fundamental functions: mobility and hold it together.

• Joints are the weakest part of the skeleton, but their structure resists various forces.

• Joints are classified by structure:

(fibrous, cartilaginous, and synovial) and function: (synarthroses,

amphiarthroses, and diarthoses).

• In general, fibrous joints are

immovable, whereas synovial are freely movable and cartilaginous have both characteristics.

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Joints:

fibrous and cartilaginous

• Bones that articulate at

fibrous joints are united by fibrous tissue, e.g. sutures.

• Syndemoses are fibrous joints that have connecting fibers that are longer than sutures, e.g. joint between tibia and fibula.

• Bone ends connected by cartilage are cartilaginous joints, e.g. pubic symphysis is an amphiarthrotic joint

whereas the joint between the first rib and sternum is a

synarthrotic joint.

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Joints:

synovial joints

• Synovial joints have articulating bone ends separated by synovial fluid.

• Synovial joints have 4 distinguishing features:

1) Articular cartilage

2) Fibrous articular capsule 3) Joint cavity

4) Reinforcing ligaments

• Flattened fibrous sacs lined with synovial fluid called bursae are associated with synovial joints as are tendon sheaths.

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Joints:

types of synovial joints

• The shapes of the articulating bone surfaces determine what movements are allowed at a joint^.

1) Plane joint are flat such as in joints of the wrist.

2) Hinge joint allows angular movement in one plane such as the elbow joint.

3) Pivot joint fits into a sleeve or ring of bone such as the atlas and dens of the axis.

4) Condyloid joint allow side to side and back and forth such as the joint of the knuckles.

5) Saddle joint allows similar movement as the condyloid joint such as the thumb.

6) Ball-and-socket joint allow rotation such as the hip joint.

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Joints:

inflammatory disorders

• Bursitis is an inflammation of bursae or a synovial membrane

• A sprain is a stretching or tearing of ligaments or tendons.

• Arthritis can be caused by over 100 different inflammatory or degenerative disorders.

• Acute forms result from bacterial invasion whereas chronic forms include osteoarthritis,

rheumatoid arthritis, or gout.

osteoarthritis

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Developmental Aspects of the Skeleton

• The skeleton changes throughout life but the most dramatic

changes occur during childhood.

• The skull develops rapidly between 6-11 years.

• The secondary curvatures are the result of the reshaping of intervertebral discs.

• During youth body proportions change as does the size of the skeleton.

• Osteoporosis is a bone thinning disease that inflicts both men and women in their 60 and 70s.

• Causes of osteoporosis include diet, smoking, and lack of

exercise.