how long approx is the small intestine?

name the 3 main parts of the small intestine

2.5 - 3 metres long!

the first 30cm is the duodenum, then the jejenum and the ileum

the duodenum

covered with viili each which have numerous microvilli known as the 'brush border' here you'll find capillaries and lymphatic vessels. the total area avilable for absorbtion and digestion is 300 m²

the pancrease is about 20cm long and weighs ~100g.

the acinar cells which are exocrine cells make digestive enzymes

chymotrpsin, trypsin, carboxypeptidase and elsatase are all synthesised in the pancreas as zymogens

they make bicarbonate

other enzymes include pancreatic amylase (starch) lipase (fats) proteases, DNase, RNase

Acinar = exocrine

Islets of Langerhans = endocrine

Alpha cells - Glucagon to stimulate glycogen ---> glucose

Beta cells - Insulin to stimulate glucose ---> glycogen

S cells - Somatostatin to regulate digestion, absorbption and release of other hormones.

with regards to absorbtion, how are monosaccharides and amino acids transported?

which salts help to emulsify fats?

they are transported into the blood capillaries of villi then to the liver via the hepatic portal vein

Bile salts help to emulsify fats. they are then suseptible to digestion by pancreatic lipase.

monosaccharides, amino acids, electrolytes and water absorbed from the intestines travel to the liver via which veins?

how do they enter the general circulation?

mesenteric veins and the hepatic portal vein

they can then enter the general circulation via the hepatic circulation

bile pigments

bile salts are stored in the gall bladder

cholesterol derivative

bile salts are amphipathic structures. They do not digest fats but act as detergents to break them down into small droplets or 'micelles' The droplets are then amenable to digestion by lipases

fatty acids and monoglycerides from fat digestion are absorbed and synthesised into triglycerides which are then packed into chylomicrons

After exocytosis, chylomicrons enter the lacteals and into the lymphatic system

the colon

it is composed of the ascending, transverse, descending and sigmoid colons. there is no digestion here and little absorbtion of nutrients

the first 3 segments absorb water and inorganic ions. the sigmoid colon is a storage depot

it is ejected through the rectum and anus (internal and external anal sphincters)

extra on colon: the acsending, transverse and descending colon lead to the sigmoid colon and the rectum and anus

pH 2 or acidic environments

those enzymes found in the intestines are active at slightly alkaline pH

help convert polypeptides into smaller peptides in the lumen of the small intestine

aminopeptidase & carboxypeptidase convert smaller polypeptides to amino acids also in the the lumen of the s.intestines.

what helps fat globules turn into fat droplets?

how do we get these droplets into glycerol and fatty acids?

in response to aroma, taste, sight or thought of food the nervous system stimulates which secretions?

which phase is this? How long does it take?

it stimulates nervous system and salivary secretions

(olfactory receptors, taste buds -> hypothalamus -> vagus nerves)

this phase is the cephalic or reflex phase and takes a few minutes

It uses acetylcholine, histamine & gastrin

Gastrin is a peptide hormone made by stomach G cells and together these 3 molecules stimulate secretion of HCL & pepsinogen

Intestinal gastrin

BUT continued release of Chyme inhibits gastric activity due to secretion by duodenum of gastric inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), cholecystokinin (CCK) and secretin

inhibition of gastric acid secretion

induce smooth muscle relaxation

stimulates pancreatic bicarbonate secretion

stimulates the digestion of fats and proteins

also acts as a hunger suppressant

ENDOCRINE glands

It secretes bicarbonate and other enzymes through exocrine glands