Digestive System

Oral Cavity

Tongue

Teeth

Salivary Glands

sublingual gland

submandibular gland

parotid gland

pharynx

site of voluntary food ingestion

assist in swallowing and mixing; involved in the buccal phase of deglutition, through the voluntary contraction of

assists in mastication to mechanically breakdown food

secrete salivary amylase, which starts the process of breaking down starches

passage way for food

esophagus

flat muscular tube that is collapsed when not performing PERISTALSIS. Peristalsis is the distal movement of food through alternating contracting and relaxing segments of the alimentary canal

stomach

contains the gastroesphageal sphincter, keeps orfice closed when food is not being swallowed and contains mucus cells to protect the esophagus from stomach acid. Controlled by the swallowing center in medulla and lower pons

Has a muscosal barrier to protect itself from the stomach acid. This layer contains a thick layer of mucus, tight junctions between cells, and has the ability to quickly replace damaged epithelial cells

Storage tank that can expand from 50 mL to 4 L.
Turns bolus --> chyme

Propulsion through peristalsis. Mechanical breakdown through churning and pummeling of chyme through the muscularis externa circular, longitudinal and oblique smooth muscle layers.

Digestion: pepsin starts enzymatic digestion of proteins. HCl unfolds proteins to prepare for the SI. Lingual and gastric lipase beings fat digestions, but is only a minor contribution to the breakdown of fat.

absorption of lipid-soluble alcohol and aspirin occurs here

small Intestine: major organ of digestion and absorption

Large Intestine

Rectum: function is defecation

Anal Canal: the last segment of large intestine. about 3 cm long; function: defectation

Anus : opening to the bodies exterior; Function: defecation

Ascending Colon

Tranverse Colon

Descending Colon

Sigmoid Colon

Structure: provides increased surface area for absorption

Villi

Circular folds

Microvilli

Finger-like projections of the mucosa. Absorbes nutrients and electrolytes. Each contains capillaries and lymphatic capillaries called lacteal

Intestinal Crypts

Goblet Cells

Duodenum

Jejunum

Ileum

deep, permanent folds of mucosa and submucosa

long densely packed cytoplasmic extensions of the absorptive cells of mucosa called the brush boarder that contain enzymes. These enzymes complete digestion of carbohydrates and proteins

Mucus secreting cells

Enterocytes

enteroendocrine cells

Paneth Cells

Stem Cells

simple columnar absorptive cells bound by tight junctions; bare primary responsibility is absorbing nutrients and electrolytes; secrete intestinal juices.

source of enterogastrones: secretin and cholecystokinin (CCK)

deep in crypts , provides the small intestine with protection by releasing antimicrobial agents such as defenses and lysozyme which destroy bacteria.

in depths of crypts; continuously dividing and differentiate into other cells types; villus epithelium renewed every 2-4 days.

Digestion Process:


Mechanical Breakdown through propulsion: segmentation by smooth muscle, mixing contents with intestinal juices. Uses short peristaltic waves moving food along tract.


Digestion: enzymes delivered from pancreas and brush board enzymes attached to microvilli membranes complete digestion of all classes of food.


absorption: breakdown products of carbohydrates, proteins, fat, nucleic acid, vitamins, electrolytes, and water through active and passive transport.


Bile from liver emulsifies fats for digestion of lipids and fat-soluble vitamins.

Digestive Process: digestion: some food is remaining and are digested by gut bacteria (some produce Vitamin K and B vitamins). Absorption: absorbs most of remaining water, electrolytes and vitamins produced by bacteria. Propulsion: propels feces toward feces. Defecation: reflex triggered by rectal dissension; eliminates feces from the body. temporarly stores until dedication can occur.

travels up the right side of the abdominal cavity

travels across the abdominal cavity

down the left side of of posterior abdominal wall

S-shaped and joins the rectum

Anal Sphincters

Internal Anal Sphincter

External Anal Sphincter

composed of smooth muscle; is involuntary controlled

composed of skeletal muscle; is voluntary controlled

Accessory Organs:

Liver:

Gallbladder:

Pancreas:

secretes bile

secretes digestive enzymes that break down all categories of foodstuff

process bloodborne nutrients in various ways like storing glucose as glycogen and use amino acids to make proteins

store fat-soluble vitamins

detoxification such as converting ammonia to urea

a thin-walled muscular sac that may appear green with filled with bile

stores bile that is not immediately needed for digestion

yellow-green, alkaline solution that contains bile salts, bile pigments, cholesterol, triglycerides, phospholipids, and electrolytes

only bile salts and phospholipids aid digestive process

bile salts go through enterohepatic circulation to recycle 95% of it

these enzymes include proteases (for proteins), amylase (for starch), lipases (for fats) and nucleases (for nucleic acids

Hormones-

Hormones

Cholecystokinin released from duodenum of small intestine inhibits secretions in the stomach, stimulates the gallbladder to contract, and increases pancreatic juice production in the pancreas

Secretin is produced in the duodenum of the small intestine and it acts on the liver to increase bile output, the stomach to inhibit gastric gland activity, and the pancreas to increase pancreatic juice production

Motilin is made in the duodenum of the small intestine and it acts on the small intestine to initiate the migrating motor complex (MMC)

Gastrin produced in the stomach mucosa stimulates contractions in the small intestine and relaxes ileocecal to allow chyme to pass from the stomach to the small intestine

Somatostatin is produced by the stomach and the small intestine. It inhibits pancreatic secretions, inhibits blood flow in the GI tract, inhibits bile release in the gall bladder, and inhibits gastric secretions

Somatostatin (shared production with the stomach)

Reflexes

Enterogastric Reflex- prevents acid secretion in the stomach

Gastroileal Reflex- strengthens the process of segmentation in the ileum and relaxes ileocecal valve

Reflexes

Gastrocolic Reflex- Stimulates contractions in the large intestine, triggered by the presence of food in the stomach

Reflexes

Defecation Reflex- stimulated by stretching of the rectum, it causes the rectum to contract and the anal sphincter to relax

Serotonin- stimulates contraction of stomach muscle

Histamine- Activates parietal cells in stomach mucosa to produce HCl

Appendix

A subdivision of the large intestine

contain masses of lymphoid tissue and as part of MALT it plays an important role in body immunity, also serves as a storehouse of bacteria

This concept map was created by: Sarah Hershey, Vivian Bui, Emma Armington, and Hannah Slaga