Digestive System

what makes up the GI tract

oral cavity, most of pharynx, esophagus, stomach, small and large intestines

what are the accessory digestive organs

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

layers of GI tract

mucosa, submucosa, muscularis, serosa

purpose of muscularis mucosae in mucosa

causes folds which increase local movements increasing absorption w exposure to new nutrients

what GI tract sections have skeletal muscle aka voluntary control

mouth, pharynx, upper esophagus, anus

bolus

ball-like mixture of food and saliva that forms in the mouth during the process of chewing

where does chemical digestion start

mouth bc of saliva

where lipase is secreted from

under the tongue

chyme

gastric juices, saliva, food

pepsin function

begins digestion of proteins

intrinsic factor function

aids absorption of vitamin B12

gastric lipase function

aids in digestion of triglycerides

gastrin function

regulator of gastric acid/juice

what converts pepsinogen into pepsin

HCL hydrochloric acid

how lacteals get to right atrium

**liver slide talking about deoxygenated and oxygenated blood**

bilirubin definition

waste product, yellow in pigment produced from breakdown of heme group from the hemoglobin molecule found in RBCs

what type of tissue in mouth, esophagus, and anus

stratified squamous which is tough tissue

parts of the mucosa

epithelium, lamina propria, muscularis mucosae

epithelium mucosa composition

tough stratified squamous in mouth esophagus and anus and simple columnar everywhere else

epithelium mucosa function

secretes enzymes and absorbs nutrients, goblet cells secrete mucus onto cell surface, enteroendocrine cells secrete hormones controlling organ function

submucosa composition

loose connective tissue containing BV, glands, and lymphatic tissue

Meissner’s plexus responsibility

in submucosa, parasympathetic innervation, vasoconstriction, local movement by muscularis mucosa

muscularis composition

skeletal muscle, smooth muscle, auerbach’s plexus

why muscularis is important

third layer of GI tract, skeletal muscle allows voluntary swallowing and defecation, smooth muscle involuntary control mixing crushing and propelling food, and Auerbach’s plexus innervates circular and longitudinal smooth muscle layers

smooth muscle of muscularis function

inner circular fibers and outer longitudinal fibers, mix crush and propel food via peristalsis

serosa location

covers all organs and walls of cavities not open to outside of body

serosa function

secretes slippery fluid

serosa composition

CT covered w simple squamous epithelium

* an example of a serous membrane

enteric nervous system (ENS)

brain of the gut controlling motility, secretions, chemoreceptors, and mechanoreceptors

Auerbach’s Plexus

longitudinal and circular smooth muscle layers of the muscularis controlling motility for both sympathetic and parasympathetic innervation

peritoneum parts

parietal peritoneum in abdominal cavity and visceral peritoneum acting like serosa to select organs

peritoneum significance

largest serous membrane of body containing large folds

greater omentum

peritoneum section draping over transverse colon and coils of the small intestine like a fatty apron

falciform ligament

attaches the liver to the anterior abdominal wall & diaphragm

lesser omentum anatomy

arises as an anterior fold of the serous of the stomach and duodenum connecting the stomach and duodenum to the liver

lesser omentum passageway

passageway for hepatic portal vein, common hepatic artery, and common bile duct

mesentery

binds the jejunum and ileum of the small intestines to the posterior wall

mesocolon

bind the transverse colon and sigmoid colon of the large intestine to the posterior abdominal wall

oral cavity function

initial phases of mechanical and chemical digestion begin and sensing food in it

roof of oral cavity

roof made of hard bones separating mouth from nasal cavity and soft palate projecting from hard palate that seperates mouth and pharynx

lateral boundaries of oral cavity

cheeks made of buccinator muscles & oral mucosa

teeth attached to jaws but not part of it

oral cavity floor

tongue

anterior boundary of oral cavity

lips w vermillion border & incisor and canine teeth

tongue composition

skeletal muscle covered w mucous membrane

teeth anatomy location

embedded in the alveolar sockets of the maxilla and mandible

number of deciduous, baby teeth

20 deciduous erupting in first or second year

classes of teeth

incisors, canines, premolars, molars

molars

large teeth with four to five cusps adapted for crushing

premolars

most circular teeth with two cusps adapted for tearing (don’t exist for babies)

canines

pointed piercing teeth lateral to the incisors and have one root each

incisors

chisel shaped teeth for cutting in midline of jaw

lamina propria in mucosa composition

thin layer of loose CT containing BV and MALT lymphatic tissue

where are MALT lymphatic nodules

in mucosa of GI tract and in tonsils, appendix

muscularis mucosae in mucosa composition and function

thin layer of smooth muscle causing folds in mucosa that increase local movement increasing absorption of nutrients

salivary gland functions

soften and lubricate food, begin chemical digestion, taste, clean mouth to keep bacteria population regulated

types of salivary glands

intrinsic/minor and extrinsic/major

pharynx & esophagus digestion function

transport but NO digestion

where esophagus pierces the diaphragm

hiatus which can turn into a hiatal or diaphragmatic hernia

stomach location

large distensible muscular sac left upper abdomen immediately below the diaphragm

what forms chyme

stomach mixes saliva food and gastric juice

what attaches liver to anterior abdominal wall

falciform ligament

neural regulation digestive hormones

gastrin, secretin, CCK, somatostatin, histamine, serotonin, gastric inhibitory peptide

where is gastrin secreted from

G cells of the gastric glands in the stomach and intestinal glands in the duodenum

when is gastrin secreted

presence of peptides and amino acids as well as stomach distension

what does gastrin do

stimulates parietal cells in the gastric glands to secrete (HCL), stimulates motility of the stomach, relaxes the pyloric sphincter

what releases secretin

S cells of the intestinal glands in the duodenum

when is secretin released

when the pH in the small intestine is acidic it also prompts bile ducts to secrete more bile

what secretin does

stimulates pancreatic cells to secrete bicarbonate, the liver to produce bile & inhibits gastric motility and gastric juice secretion

what secretes Cholecystokinin (CCK)

CCK cells of intestinal glands in duodenum

when is CCK secreted

presence of lipids and polypeptides in small intestine

what CCK does

stimulates the pancreatic cells to secrete pancreatic juice, the release of bile from the gallbladder, and relaxes the hepatopancreatic ampulla sphincter

what secretes gastric inhibitory peptide

K cells in the intestinal glands of duodenum and jejunum

when is gastric inhibitory peptide secreted

presence of lipid and glucose in the small intestine

what does gastric inhibitory peptide do

release of insulin & inhibits gastric juice secretion and gastric motility

what secretes somatostatin

D cells of the stomach, intestine, and pancreas

what does somatostatin do

inhibits the secretion of gastrointestinal hormones, most importantly gastrin and histamine

what secretes histamine

enterochromaffin cells (histaminocytes) of stomach mucosa

what does histamine do

stimulates parietal cells to secrete hydrochloric acid

what secretes serotonin

enterochromaffin cells of the gastric mucosa

what does serotonin do

causes contraction of the stomach muscles

liver functions

excrete bilirubin, synthesize bile, excrete drugs, metabolize carbs/lipids/proteins, stores vitamins A/D/B12/Fe and glycogen

what liver produces

urea, bile, heparin, vit A, plasma proteins, antibodies

liver blood supply

oxygenated blood from hepatic artery and nutrient rich blood from stomach, spleen, and intestines carried via hepatic portal vein

liver blood supply order

hepatic artery, liver sinusoids, central vein, hepatic vein, inferior VC

liver’s carb metabolism

proteins into glucose, triglycerides into glucose, excess glucose into glycogen (to store), and glycogen into glucose as needed

liver’s lipid metabolism

synthesizes lipoproteins (HDL/LDL) and cholesterol, releases energy and stores fat, breaks down fatty acids

liver’s protein metabolism

convert one amino acid into another, converts ammonia into urea, synthesizes plasma proteins from clotting/immune system

deamination

liver removes NH2 (amine group) from amino acids so we can utilize the rest as energy

how much bile is secreted by the liver

1 quart per day

bile PH and color

PH 7.6-8.6 and yellow-green color

bile components

cholesterol, Na, K, bilirubin

liver’s heme

broken down into iron and bilirubin

how is bile released from the liver

released into the duodenum via the common bile duct 

bile function

emulsify fats into micelle droplets by increasing surface area

how is bile reused

after fat emulsification, it can recycle back to gallbladder through ileum, via hepatic portal blood

what does bile synthesis stimulate

peristalsis

bilirubin and liver relationship

liver absorbs bilirubin from the blood and secretes it into the bile so it may be released into SI via biliary tree

bilirubin and LI relationship

bilirubin broken down in LI further by intestinal bacteria and excreted from the body in the feces.

drugs and kidneys

principle organs for drug excretion and their metabolites

liver and drug excretion

hepatocytes of the liver do play a small role in drug excretion by actively and passively excreting them into the bile