1.)Tube:Alimentary Canal aka Gastrointestinal (G.I) tract

from mouth to anus

2.) Accessory digestive organs and glands

-enzymes are ducted into the tube

• The visceral peritoneum is a serous membrane on the surface of the organs
• The parietal peritoneum is on the cavity walls
• The mesentary is the membrane that connects the two.

• Holds the organs in place
• Provides a route for blood vessels
• allows for fat storage and lymph nodes

inflammation of the peritoneum

*can be caused by a burst appendix and consequential bacterial infection

creates saliva which contains:

• Salivary Amilase: starts break down of starch into sugar
• Lysozyme: Destroys bacteria via antibodies and other defensive molecules
• Mucus: moistens food and helps with swallowing.

• Parotid (biggest) anterior to the ear and near the masseter muscle
• Submandibular: under the mandible in the floor of the mouth
• Sublingual: under the tongue

• 10" long tube
• passes through down thorax, through diaphragm at esophogeal hiatus and joins the stomach.
• Made of stratiified squamous epithelium
• No absorption of nutrients

Sphincter which joins the esophagus and the stomach to keep food down

Diaphragm reinforces the sphincter

If sphincter isn't working properly, results in heartburn.

• expandable holding tank until chyme is passed onto the small intestine
• start of protein digestion
• kills bacteria with HCl

• First third skeletal muscle
• second third skeletal muscle and smooth muscle
• last third smooth muscle

Folds in the inner lining

Can expand almost 100 times

Curvature at the top of the stomach

[image]

last part of stomach before it funnels into the small intestine

 [image]

Sphincter that controls chyme going into the small intestine

"gatekeeper"

The greater omentum is a mesentary that hangs from the greater curvature of the stomach

[image]

^^^^^^^^

Greater Omentum

A mesentary that hangs from the lesser curvature and attaches to the liver

[image]

All smooth muscle

Outer: Longitudinal layer 

Middle: Circular Layer

Inner: Oblique Layer

** Stomach is only part of the G.I. tract to have the oblique layer

secretes alkaline mucus:

protects against stomach against stomach acid

has gastric pits which are the openings to the gastric glands

Mucous neck cells

parietal cells

Chief cells

enteroendocrine cells

simultaneously secretes:

HCl acid to break down food and kill bacteria

Intrinsic Factor for Vitamin B₁₂ absorption

the inactive form of the protein-degestin enzyme pepsin.

pepsinogen is activated by HCl in the stomach

secrete chemical messengers and hormones:

Histamine: chemical messenger that acts locally to stimulate paracrine cells to secrete HCl

Gastrine: increases stomach motility as well as stomach secretions

• Thick alkaline mucous neutralizes acid
• Tight junctions of eepithelial cells prevent acid from seeping in
• Constant replacement of epithelial cells

Smalll amount of protein digestion

Absorption: only alcohol and aspirin because they are lipid soluble

Intrinsic factor in order to absorb vitamin B12

• Duodenum: 1st 10 inches
• Jejunum: 8ft
• Ileum: 12 ft

Where the Bile duct from the liver joins the pancreatic duct from the pancreas and they unite at the wall of the duodenum of the small intestine.

[image]

• The tube is very long
• Plicae Circularis: circular folds
• Villi: fingerlike projections of the innermost layer (mucosa)
• Microvilli: on the surface of epithelial cells

Fingerlike projections that have capillaries for absorbing amino acids and sugars

also contain lacteals (lymphativ capillaries) for fats

Brush border of epithelial cells

have enzymes to finish carbohydrate and protein digestion

"brush border enzymes"

break carbohydrates into disacharides-> monosacharides

ex: lactase, enteropapptidase

Brunner's glands (Duodenal glands)

secretes an alkaline mucous

Peyer's Patches: Lymphoid nodules

(to protect small intestine from bacteria that can creep in from the large intestine)

• detoxifying ammonia from amino acid breakdown
• detoxifying alcohol and drugs
• cleansing and modifying blood from the digestive system (portal circulation)
• storage of glucose, amino acids, and vitamins.
• Manufacture of plasma proteins
• Synthesizes cholesterol and packages it as HDL and LDL

HDL: High Density Lipoprotein: good cholesterol

LDL: Low Density Lipoprotein: bad cholesterol

Makes bile?

**HDL is cholesterol on the way to excretion through bile

• Right
• Left
• Caudate
• Quadrate

inferior view

[image]

• Bile leaves the liver via the hepatic duct and joins the cystic duct of the gall bladder and forms the bile duct.
• Excess bile that backs up is stored in the gallbladder.

[image]

Lobules are hexagonal shaped and contain:

• hepatocytes: liver cells
• Triads: hepatic portal vein, hepatic artery, bile duct
• Sinusoids
• Central Vein

[image]

yellow-green solution of

• bile salts
• bile pigments
• cholesterol
• fats

• Bicarbonate ion (Alkaline solution)
• Inactive proteolytic enzymes:
• chymotrypsinogen
• trypsinogen
• procarboxypeptidase
• Pancreatic Amylase
• Lipase (fats)
• Nuclease (DNA & RNA)

enteropeptidase activates trypsinogen to produce trypsin.

trypsin activates chymotrypsinogen and procarboxypeptidase

Hormonally:

CCK and Secretin

• Cecum (with its appendix)
• colon
• anal canal

• Ascending
• transverse
• descending
• sigmoid

[image]

Anal canal: 2 sphincters

internal (smooth muscle)

external (skeletal muscle)

Form and eliminate feces

Water reabsorption

Diarhea: Contents are rushes through too quickly and not enough water is absorbed

Constipation: Contents move through too slowly and too much water is absorbed.

• Synthesize some B vitamins
• Synthesize vitamin K
• prevent pathogens from growing

spinal cord mediated reflexes triggered by the movement of feces into the rectum. 

Walls of sigmoid colon and rectum contract.

We can control external sphincter and if kept closed, contractions die, but will start again after a while.