6- HUMAN PHYSIOLOGY
Diges ve system
● A long tube with two organs: pancreas and liver.
● Inges on → diges on → absorp on → transport
● Begins with the mouth and ends with the anus.
● Food has molecules that are too large to pass through cell
membranes, so they have to be chemically digested to a
smaller size (catabolism).
● Diges ve enzymes catalyse chemical reac ons occurring
during the metabolic process.
● E.g. lipase for breakdown of lipids, amylase for amylose
(starch).
● The human body maintains the temperature at 37oC, which
keeps constant molecular movement and an ideal
temperature for the enzymes to act during diges on.
Alimentary canal
● Food o en has to travel against gravity, so smooth muscles
keep food moving in the correct direc on.
● Smooth muscle is controlled by the autonomic nervous
system (ANS).
● Alimentary canal has two layers of smooth muscle: circular
and longitudinal.
● The contrac ng bres of circular muscles make a circle, while those of longitudinal muscles are
at right angles to the circular ones.
● Peristalsis → muscle mo on and food movement caused by the ac on of smooth muscles.
● It’s also used in the stomach to mix food with protein-diges ng enzymes (churning). It causes a
contrac on behind the food mass to push it through the canal.
● Peristalsis is fast in the oesophagus and slow in the intes nes.
titiftti ti fi ti ti ti ti ti ti ti ti ti
, Pancreas
● Produces insulin and glucagon, hormones needed for glucose metabolism.
● Produces 3 diges ve enzymes: amylase, lipase and endopep dase → these are part of the
pancrea c juice.
● The pancrea c duct takes par ally digested food from the stomach, adds the enzymes and bile
from the liver, and sends it into the lumen of the small intes ne.
● Lipase → lipids into glycerol and fa y acids.
● Amylase → starch into maltose (another enzyme breaks down to glucose).
● Endopep dase → long polypep de chains into smaller ones (another enzyme breaks down to
amino acids).
Small intes ne
● E.g. diges on and absorp on of starch.
● Incompletely digested starch enters the rst sec on of the small intes ne: the duodenum.
● Its pH is neutral-slightly alkaline for amylase to work.
● Peristalsis pushes the starch through the lumen as amylase catalyses the hydrolysis into maltose.
● Then the enzyme maltase breaks down maltose into glucose.
● Maltase is produced by the cells of the small intes ne’s inner lining → make up the mucosa.
● The mucosa has many folds called villi, and each is made of cells that absorb certain molecules
from the food.
● The absorp on is done by epithelial cells → they have microvilli that extend into the lumen.
● Each villus contains:
- Epithelial cells with microvilli → greater surface area for absorp on.
- Capillary bed → nutrient absorp on and transport of monomers into the bloodstream.
- Lacteal → small lympha c vessel that absorbs larger nutrients.
● Villi usually absorb water, glucose, amino acids, glycerol and fa y acids, nucleo des, vitamins
and mineral ions.
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, EPITHELIAL CELLS
1. Passive mechanisms → simple and facilitated di usion (down the concentra on gradient, no ATP
used).
2. Ac ve mechanisms → membrane pumps and endocytosis (against the concentra on gradient,
ATP used).
Blood system
● Arteries → vessels that take blood away from the heart (Arteries = Away). Arterioles are the
smallest of arteries.
- Thick and smooth muscle layer controlled by the ANS, to change the diameter of the
lumen of blood vessels.
- Elas c bres to sustain high blood pressure and to increase blood pressure when it’s
lower.
● Veins → vessels that collect blood from capillaries and send it to the heart.
- Thin walls and larger lumen diameter because the blood’s pressure has been lost when it
reaches the veins.
- ‘One-way ow’ valves keep the blood travelling in the right direc on.
● Capillary bed → network of capillaries that all drain into a single venule.
- Blood passes through capillaries one cell at a me so pressure is lost.
- Walls are thin enough for chemical exchange to occur.
Heart
● Designed as a pair of side-by-side pumps: atria and ventricles.
● Atria → receive low-pressure blood from veins, thin-walled muscular chambers.
● Ventricles → build up pressure to send blood out to arteries, thick-walled muscular chambers.
● Blood’s journey:
1. Deoxygenated blood received from
superior vena cava into the right atrium.
2. Passes into right ventricle and enters the
pulmonary artery.
3. Sent to the lungs for oxygena on and
received in heart from pulmonary veins.
4. Le atrium → le ventricle → aorta and
its branches send to the rest of the body.
5. Passes through capillary beds in organs
and ssues, to deliver oxygen and pick up
CO2.
● Right side of heart: pulmonary circula on
● Le side of heart: systemic circula on
fttititi fi fl ft ti ti ti ti ff ti ti ti
Diges ve system
● A long tube with two organs: pancreas and liver.
● Inges on → diges on → absorp on → transport
● Begins with the mouth and ends with the anus.
● Food has molecules that are too large to pass through cell
membranes, so they have to be chemically digested to a
smaller size (catabolism).
● Diges ve enzymes catalyse chemical reac ons occurring
during the metabolic process.
● E.g. lipase for breakdown of lipids, amylase for amylose
(starch).
● The human body maintains the temperature at 37oC, which
keeps constant molecular movement and an ideal
temperature for the enzymes to act during diges on.
Alimentary canal
● Food o en has to travel against gravity, so smooth muscles
keep food moving in the correct direc on.
● Smooth muscle is controlled by the autonomic nervous
system (ANS).
● Alimentary canal has two layers of smooth muscle: circular
and longitudinal.
● The contrac ng bres of circular muscles make a circle, while those of longitudinal muscles are
at right angles to the circular ones.
● Peristalsis → muscle mo on and food movement caused by the ac on of smooth muscles.
● It’s also used in the stomach to mix food with protein-diges ng enzymes (churning). It causes a
contrac on behind the food mass to push it through the canal.
● Peristalsis is fast in the oesophagus and slow in the intes nes.
titiftti ti fi ti ti ti ti ti ti ti ti ti
, Pancreas
● Produces insulin and glucagon, hormones needed for glucose metabolism.
● Produces 3 diges ve enzymes: amylase, lipase and endopep dase → these are part of the
pancrea c juice.
● The pancrea c duct takes par ally digested food from the stomach, adds the enzymes and bile
from the liver, and sends it into the lumen of the small intes ne.
● Lipase → lipids into glycerol and fa y acids.
● Amylase → starch into maltose (another enzyme breaks down to glucose).
● Endopep dase → long polypep de chains into smaller ones (another enzyme breaks down to
amino acids).
Small intes ne
● E.g. diges on and absorp on of starch.
● Incompletely digested starch enters the rst sec on of the small intes ne: the duodenum.
● Its pH is neutral-slightly alkaline for amylase to work.
● Peristalsis pushes the starch through the lumen as amylase catalyses the hydrolysis into maltose.
● Then the enzyme maltase breaks down maltose into glucose.
● Maltase is produced by the cells of the small intes ne’s inner lining → make up the mucosa.
● The mucosa has many folds called villi, and each is made of cells that absorb certain molecules
from the food.
● The absorp on is done by epithelial cells → they have microvilli that extend into the lumen.
● Each villus contains:
- Epithelial cells with microvilli → greater surface area for absorp on.
- Capillary bed → nutrient absorp on and transport of monomers into the bloodstream.
- Lacteal → small lympha c vessel that absorbs larger nutrients.
● Villi usually absorb water, glucose, amino acids, glycerol and fa y acids, nucleo des, vitamins
and mineral ions.
tititi titi ti ti ti ti titi tt fi ti ti titi ttti ti ti
, EPITHELIAL CELLS
1. Passive mechanisms → simple and facilitated di usion (down the concentra on gradient, no ATP
used).
2. Ac ve mechanisms → membrane pumps and endocytosis (against the concentra on gradient,
ATP used).
Blood system
● Arteries → vessels that take blood away from the heart (Arteries = Away). Arterioles are the
smallest of arteries.
- Thick and smooth muscle layer controlled by the ANS, to change the diameter of the
lumen of blood vessels.
- Elas c bres to sustain high blood pressure and to increase blood pressure when it’s
lower.
● Veins → vessels that collect blood from capillaries and send it to the heart.
- Thin walls and larger lumen diameter because the blood’s pressure has been lost when it
reaches the veins.
- ‘One-way ow’ valves keep the blood travelling in the right direc on.
● Capillary bed → network of capillaries that all drain into a single venule.
- Blood passes through capillaries one cell at a me so pressure is lost.
- Walls are thin enough for chemical exchange to occur.
Heart
● Designed as a pair of side-by-side pumps: atria and ventricles.
● Atria → receive low-pressure blood from veins, thin-walled muscular chambers.
● Ventricles → build up pressure to send blood out to arteries, thick-walled muscular chambers.
● Blood’s journey:
1. Deoxygenated blood received from
superior vena cava into the right atrium.
2. Passes into right ventricle and enters the
pulmonary artery.
3. Sent to the lungs for oxygena on and
received in heart from pulmonary veins.
4. Le atrium → le ventricle → aorta and
its branches send to the rest of the body.
5. Passes through capillary beds in organs
and ssues, to deliver oxygen and pick up
CO2.
● Right side of heart: pulmonary circula on
● Le side of heart: systemic circula on
fttititi fi fl ft ti ti ti ti ff ti ti ti
