small intestine

Question 1

what occurs in the duodenum, jejunum and ileum respectively?

Answer 1

most chemical digestion occurs in the duodenum, a mix of chemical digestion and absorption occurs in the jejunum, and most absorption occurs in the ileum

Question 2

what are the chemical secretions in the duodenum?

Answer 2

1. pancreatic juice secreted by the pancreas
2. intestinal juice secreted by cells of the duodenum
3. bile produced by the liver and temporarily stored in the gallbladder

Question 3

what is the function of bile?

Answer 3

bile functions to emulsify large fat droplets by physically digesting them into triglycerides, which increases surface area to volume ratio, increasing the rate of lipid hydrolysis later on by lipase

Question 4

how are digested food substances absorbed?

Answer 4

they are absorbed by diffusion and active transport

Question 5

what are the factors that affect the rate of absorption of digested food?

Answer 5

1. surface area to volume ratio
2. diffusion distance
3. concentration gradient

Question 6

what is the function of a long small intestine

Answer 6

it allows for a large total surface area present for absorption and its length allows sufficient time for absorption of nutrients

Question 7

what is the function of many folds on the surface of the small intestine, presence of villi and individual epithelial cells of the villi

Answer 7

it allows for a larger surface area to volume ratio of the surface, which increases absorption rate of digested substances

Question 8

what is the function of the epithelium of vii being one cell thick

Answer 8

it allows for a short distance for digested nutrients to travel, and thus a shorter time is required for the absorption of nutrients, increasing the rate of digested food substances

Question 9

what is the function of a rich network of capillaries and the presence of blood capillaries and lacteal in villi

Answer 9

absorbed nutrients are quickly transported away from the digestive system, which helps to maintain a steep concentration gradient between the lumen of the small intestine and its blood supply

Question 10

how are nutrients transported in the small intestine

Answer 10

glycerol and fatty acids enter the epithelial cells during absorption via diffusion, and are subsequently transported away via the blood capillaries. capillaries in the villi combine to form the hepatic portal vein which transport blood rich in nutrients from the small intestine towards the liver