Human Anatomy III:
Respiratory, Urinary & Digestive
Systems
The Respiratory System
Major functions include: Obtaining oxygen
Removing carbon dioxide
Maintenance of pH balance
Respiration may be accomplished in a variety of ways
Animals small enough use diffusion; no specialized organs
Directly through the skin (again, via diffusion)
Gills (for aquatic animals)
Tracheal tubes (insects)
Lungs (terrestrial vertebrates)
Clockwise from upper left: tracheae in a grasshopper; book lungs in a spider; tracheal gills in an aquatic insect larva
Basic Anatomy of the Respiratory
System I
Air enters through the
nose
Inside nose the air is warmed and moistened
From the nose it enters the
pharynx
Junction point where oral and nasal passages meet
It then passes over the
larynx
, or
voice
box
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Basic Anatomy of the Respiratory
System II
The Alveoli
Alveoli are the capillaries of the lung; gas exchange occurs here rather than in bronchi or bronchioles
Oxygen moves out of the alveoli
Carbon dioxide moves into the alveoli
Alveoli resemble a bunch of grapes at the end of bronchioles
Each alveolus is covered in a thin film of water and a surfactant
Gas exchange can’t occur without water
Surfactants keep an alveolus from sticking to itself and collapsing during breathing
The
Pleural Cavity
The lungs sit within a space called the pleural cavity
Normally, the outer surface of the lungs sticks to the inner surface of the pleural lining
Puncturing the cavity causes a
pneumothorax Air gets in and lungs
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Breathing:
Inspiration
In the first part of breathing, air is taken into the lungs
This is an active process and occurs when:
The diaphragmis lowered
The rib cage expands
These two steps increase the lung volume, which lowers the pressure within the lungs compared to the outside pressure
Thus, air moves in!
Breathing:
Expiration
In the second part of breathing, air is pushed out of the lungs
This is a passive process and occurs when: The diaphragmis raised
The rib cage contracts
These two steps decrease the lung volume, which raises the pressure within the lungs compared to the outside pressure
Thus, air moves out!
Normal breathing rates in humans are 12-20 breaths per minute
Respiration in Birds
Most vertebrates mix incoming and
outgoing air
Thus, some oxygen is lost and some
carbon dioxide retained
Birds have a unique breathing pathway
to avoid this
Air flows in only one direction
Involves a number of air sacs to store air
before or after it goes to lungs
Respiration in Fishes
Most fish exchange gases primarily with gills (a few have lungs)
Use counter-current exchangeto increase efficiency
Water has less oxygen than does air
Blood and water flow in opposite directions
The Urinary System
Major functions are:
To rid body of waste material, primarily excess water, excess ions, and nitrogenous waste
To maintain fluid and ion balance
To maintain pH balance
To maintain blood volume
In humans, ureais the nitrogenous waste product
Formed when proteins are broken down
The urinary system forms part of the excretory system, along with the lower part of the digestive system
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Basic Anatomy of the Urinary System
Kidneyslie along the rear of the body, oneither side of the spine
Kidneys filter the blood and produce a mix of water and waste called urine
The ureteris a tube which connects the kidneys and…
The bladderis a muscular storage organ which holds the urine
Can hold up to 800 ml under normal conditions
Urine leaves the bladder and exits the body through the urethra
In males, urethra also connects to reproductive
organs; not true in females Most non-mammals have a common exit for the excretory and reproductive systems called the cloaca
Urine Formation
Blood from capillaries is first filtered and
the resulting fluid collected (in the
glomerulus
and
Bowman’s capsule
)
This fluid moves through a series of tubes
(the
proximal and distal tubules
, the
loop
of Henle
)
Water and ions are reabsorbed as needed by diffusion or active transport
Capillaries around tubules gather up reabsorbed water and ions
Finally, fluid exits nephron and collects in
renal pelvis
Kidney Stones
Stones result from a buildup of material in the renal medulla
Usually made of calcium oxalate crystals
If large enough (above 2-3 mm) cause pain as they move through ureter
Usually painless after they reach bladder
Control of the Urinary System
Several hormones control rate of water retention in the kidneys
Most important of these is antidiuretic hormone, or ADH
ADH increases reabsorption of water by making the tubules more “leaky”
Diuretics, such as caffeine, can interfere with these hormones
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The Digestive System
Major functions are:
To break down large food particles and absorb nutrients
To excrete solid waste material (feces)
To help maintain water balance
More primitive animals have a digestive system where food and wastes move through the same opening (the gastrovascular cavity)
Most animals have a digestive system where food enters and wastes exit through separate openings (a complete digestive system)
The Journey of a Food Bolus!
Digestion begins with the mouth
Teeth mechanically break down large bites into small pieces
Adult humans have 32 teeth
8 incisorsto cut or tear
4 cuspids(canines) for cutting
8 premolars(bicuspids) and 12 molarsfor crushing
Carbohydrate breakdown begins due to amylase
produced by salivary glands
After this, food moves into the pharynx via the process of swallowing
The Journey of a Bolus II!
The Stomach
Further breaks down food, mainly carbohydrates and proteins, to produce chyme
Stomach possesses sphinctersat either end to prevent backflow into throat or early entry to intestines
Cardiac (lower esophageal) sphincter to throat
Pyloric sphincter to intestines
Lining of stomach is heavily folded into rugae Cells in rugae make hydrochloric acidand pepsin(an
enzyme to break down proteins
pH of stomach is usually 2 (no food) to 4 (with food)
Also produces amylases
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The
Pancreas
Lies near the stomach and connects to duodenum
Produces a large amount of digestive enzymes which enter small intestine
Amylases for carbohydrates
Proteases for protein
Lipases for lipids (fats)
Also produces the hormones insulin and glucagon, which help regulate blood sugar levels
The
Liver
Largest organ by weight in the body
Produces bile, which is stored in the gall bladder
or enters SI
Bile helps break apart fat globules so that lipase can act on them to break them down
Converts and stores simple sugars to regulate blood sugar level
Completes breakdown of proteins to amino acids and urea
Removes toxins from blood
Liver is made up of around 100,000 lobules, which filter blood from intestines
The
Large Intestine
Thicker and shorter (~1.5 m) than small intestine
Aids in reabsorption of water
About 95% of water entering intestines is reabsorbed
Absorption of some material Assisted by a dense gut flora (bacteria)
These also produce several vitamins (K, B5)
Compaction and excretion of solid waste material
Largest segment is the colon
Cecumis a pouch-like region that attaches to small intestine
Rectumis the muscular tube that exits body at the anus
