Chapter 26- Digestive System Lecture

salivary glands, liver, gallbladder, pancreas, teeth, and tongue

4 layers

mucosa- epithelium, lamina propria, and muscular mucosa. is the first line of defense

submucosa- blood/lymph vessels, nerves, mucus secreting glands, MALT, and peyers patch in the S.I

muscularis- consists of an inner (circular fibers to form sphincters), and an outer (longitudinal fibers) to create contractions throughout GI tract

wave-like contractions that propel materials through the GI tract (milking contents towards the colon)

blends the ingested materials and secretions of the GI tract together with ring-like contractions

serosa- made of CT as the outermost layer

in the peritoneum, which is lined by the serous membrane

• visceral attaches to organs, and parietal is the outermost lining

it promotes GI tract activity by increasing motility and relaxing sphincters

it inhibits GI tract activity by decreasing motility and contracting sphincters

mechanoreceptors detect if there is any food at all stretching the organs of the digestive system, where as chemoreceptors detect what kind of chemicals are in the food being digested.

1. gastrin- from the stomach

2. CCK (cholecystokinin)- from the SI

3. secretin- from the SI

food is ingested and masticated

1. parotid- located behind ear and duct empties by the ear

2. sublingual- duct empties under the tongue also where it is located

3. submandibular- duct empties under the jaw, also where gland is located

salivary amylase, IGA, mucus, lysozyme. acts as first line of defense

1. voluntary phase- in oral cavity passing oropharynx

2. involuntary phase 1-passes the entirety of the pharynx

3. involuntary phase 2- passes by the esophagus allowing larynx come up and close epiglottis

at the esophageal hiatus, the inferior esophageal sphincter allows the bolus to move in to the stomach and prevent regurgitation

L gastric artery from the abdominal aorta and the R gastric artery from the hepatic artery create an anastomoses

1. cardia- inferior esophageal sphincter entryway

2. fundus- like a superior dome

3. body- central area

4. pylorus- pyloric sphincter exit way

*THINK: Can Freddy Buy Pickles?

5

they secrete alkaline mucin that protects stomach lining from acid

they secrete acidic mucin helps contributes some acidity in the stomach

they secrete intrinsic factor which helps to absorb vitamin B12, as well as H+ and Cl- to form HCl within the stomach to form the acidic enviornment of the stomach

they secrete pepsinogen which is the inactive form of enzyme pepsin which breaks down big proteins, as well as gastric lipase which can only function in more neutral environments so it has a limited role

they secrete gastrin which is a hormone sent to the brain to stimulate chief and parietal cell activity and muscular contraction of the stomach

1. cephalic phase- in this phase sensory input of food allows the medulla oblongata/hypothalamus to stimulate the stomach to increase force and speed of contractions

2. gastric phase- initiated by food in the stomach, baroreceptors detect stomach stretch and chemoreceptors detect chemical intake allowing stomach contractions to continue

3. intestinal phase- initiated by the Prescence of acidic chyme in the duodenum, this lower pH will send less hunger signals to the brain which will slow down contractions and stomach secretions

1. duodenum- shortest, but receives acidic chyme from the stomach, bicarb and juices w/enzymes from pancreas, and bile from gallbladder

2. jejunum- chemical digestion making big macromolecules smaller

3. ilium- absorption of digested nutrients. ileocecal valve at the end sending contents to large intestine.

the SI contains villi formed by microvilli making a brush border. the simple columnar epithelium in each villi as well as blood/lymph capillaries inside allow substances to be absorbed. enzymes can be secreted from here too

CCK, secretin, mucus, H2O, enzymes from the microvilli breaking down small polymers into monomers.

the liver produces bile, then drained to the gallbladder for storage and released into the duodenum.

bile allows for emulsification to occur which is the only way lipids can be digested

when blood glucose is high, excess glucose can be placed into glycogen reserves

when the reserves of glycogen are too full, so the glucose must be stored as fat.

when blood sugar is low, glucose breaks out of glycogen reserves and is sent to blood

when your body has to make new glucose out of protein

vitamin/mineral storage, detoxification of alcohol, phagocytosis of RBCs and synthesis of plasma proteins

stores and concentrates bile, by being secreted via the cystic duct into duodenum

secretes pancreatic juice for digestion in the duodenum, being released via the pancreatic ducts

bicarb to neutralize incoming chyme, and enzymes for digestion

finishes the job of stomach pepsin by breaking down large polypeptide chains into small polypeptide chains before brush border enzymes make small polypeptides into a monomer

pancreatic amylase breaks down starches and carbs from larger polypeptide chains into smaller polypeptide chains

help to breakdown fats after they have been emulsified by bile into fatty acids and glycerol

CCK- secreted from SI and regulates the pancreas to by increasing pancreatic juice release and gallbladder contraction

Secretin- is secreted by the SI and regulates the pancreas to increase bicarb release

1. cecum

2. ascending colon

3. transverse colon

4. descending colon

5. sigmoid colon

6. rectum

7. anus

pockets in the large intestine that help to move materials through

they help digest remaining nutrients, produce vitamin K, breakdown remnants that contribute to feces odor and color

H2O, salt, sloughed off epithelial cells, undigested foods and bacteria

high fiber in your diet allows for an increased size bulk, so the colon to stretch further stimulating colon movements

1. internal anal sphincter- under involuntary control

2. external anal sphincter- under voluntary control

amino acid moves into the cell through a symporter driven by sodium potassium pump. then they move out of the cell and enter the capillaries of the intestinal villi and go to the liver via hepatic portal vein

monosaccharides moves into the cell through a symporter driven by sodium potassium pump. then they move out of the cell and enter the capillaries of the intestinal villi and go to the liver via hepatic portal vein

emulsified fats from bile become micelles and enter the intestinal cell through simple diffusion. once they are in the cell, they become separated into glycerol and fatty acid and combined into a triglyceride. Proteins will come and coat the triglyceride to make it water soluble, and go through the lymphatic system to the left subclavian vein where they are later stored by the liver as adipose tissue