Digestive System

Digestive Tract

Oral Cavity

Pharynx

Esophagus

Stomach

Small Intestine

Large Intestine

Rectum/Anus

Accessory Organs

Salivary glands

Liver

Gallbladder

Pancreas

Digestive System Functions

Ingestion

Secretion

Digestion

Absorption

Elimination

Secretion

producing and releasing mucin and fluids such as acid, bile, and enzymes

Digestion

Breakdown of large food items into smaller structures and molecules

Absorption

passive or active transport of electrolytes, digestion products, vitamins, and water across GI tract epithelium and into the GI tract blood and lymph vessels

Elimination

undigestible materials is compacted into feces and then eliminated via defecation

Mechanical Digestion

Physically breaks down ingested material into smaller pieces

Chemical Digestion

breaks down ingested materials into smaller molecules using enzymes

Peritoneum

abdominal organs are supported by serous membranes that suspend organs from posterior abdominal wall and secrete lubricating fluid

Parietal Peritoneum

lines body walls

Visceral Peritoneum

covers organs

Peritoneal Cavity

potential space where layers of peritoneum that face each other secrete lubricating fluid

Mucosa

innermost layer

divided into epithelium, lamina propria, muscularis mucosa

Submucosa

loose connective tissue

nerves, arteries, veins, and lymphatics travel through this layer

Muscularis

2 or more layers of smooth muscles

Adventitia/Serosa

connective tissue that either connects to another organ or is part of the peritoneum

Palate

part of oral cavity

forms superior boundary, separates from nasal cavity

Anterior 2/3 hard and bony

Posterior 1/3 soft and muscular

Cheeks

form lateral walls of oral cavity and contain buccinator muscle

Lips

form anterior wall

red from superficial blood vessels

reduced keratin

Tongue

formed from skeletal muscle and covered with stratifies squamous epithelium

papillae with taste buds cover surface

Functions of Saliva

moistens ingested food for easier swallowing

moistens, cleanses, and lubricates oral cavity structures

amylase=enzyme that helps break down food

lysosyme= enzyme that helps inhibit bacterial growth

dissolves tastants and food molecules so that taste receptors can be stimulated

Mucous Cells

type of salivary gland cells

secrete mucin

secretion stimulated by parasympathetic division of ANS

Serous Cells

type of salivary gland cells

secrete watery fluid with ions, lysozyme, and salivary amylase

secretion stimulated by parasympathetic division of ANS

Sublingual Gland

one of the three salivary glands

inferior to tongue

Parotid Gland

one of three salivary glands

largest, located anterior and superior to ear

Submandibular Gland

inferior to body of mandible

Pharynx

3 regions

nasopharynx

oropharynx

laryngopharynx

Pharyngeal Constrictor Muscles

contract sequentially pushing material down toward esophagus

Esophagus

muscular, tubular passageway from pharynx to stomach

passes through whole in diaphragm called esophageal hiatus

Fundus

part of stomach

dome-shaped region lateral and superior to the esophageal connection

Cardia

part of stomach

narrow superior entryway into stomach from esophagus

Pylorus

part of stomach

narrow, medially directed region that forms termination of stomach

Body

part of stomach

largest region

inferior to cardiac orifice and fundus

Pyloric Sphincter

part of stomach

leads to duodenum

Mucus Cells

secretion: Mucin

function: protection of epithelium from acidic secretions

Parietal Cells

Secretion: hydrochloric acid and intrinsic factor

Functions: denatures proteins and helps bind vitamin B12

Chief Cells

Secretion: enzymes

Function: digestion

Enteroendocrine Cells

Secretion: Gastrin

Function: hormone that stimulates secretion of other stomach cells

Small Intestine

finishes chemical digestion

absorbs up to 90% of the nutrients and water from GI tract

blood supply is superior mesenteric artery

3 regions: duodenum, jejunum, ileum

Duodenum

C-shaped region that arches around pancreas

receives bile and pancreatic juices

Jejunum

middle region

primary region of chemical digestion and absorption

Ileum

distal region

terminates at ileocecal valve= sphincter that controls entrance into large intestine

Circular Folds

histology of small intestine

form from mucosa and submucosa

increase surface area

slow down food

Villi

project from the mucosa to increase surface area

Porta Hepatis

area where blood vessels and bile ducts enter and leave liver

Hepatocytes

liver cells

produce bile and secrete into bile duct

detoxify drugs, metabolites, and poisons

store excess nutrients and vitamins and release when needed

synthesize blood plasma proteins such as albumins, globulins, and proteins required for clotting

arranged in hepatic lobules

Portal Triad

located at the periphery of each hepatic lobule

contains an artery, vein, and bile duct

Branches of hepatic portal vein

carries blood from GI tract to liver

rich in nutrients and other absorbed substances

relatively poor in oxygen

Hepatic artery

branch of celiac artery

carries oxygen-rich blood to capillary beds in liver, which then leave as venous blood

Branches of bile duct

bile is greenish fluid that breaks down fats and is produced by hepatocytes

released to duodenum via common bile duct

Gallbladder

attached to inferior aspect of liver

saclike organ that concentrates and stores bile

connected to common bile duct via cystic duct

sphincter valve controls flow of bile into and out of gallbladder

Pancreas

has head, body, tail

head is cupper by duodenum

exocrine portion secretes digestive enzymes and bicarbonate (called pancreatic juice)

secretes pancreatic juice into main pancreatic duct → drains into major duodenal papilla in duodenum

Major Duodenal Papilla

both the common bile duct and the main pancreatic duct empty into duodenum via this structure

Large Intestine Function

absorbs most of the water from digested material to solidify material into feces

Movement of Large Intestine

Cecum → Ascending Colon → Hepatic Flexure → Transverse Colon →Splenic Fixture → Descending Colon → Sigmoid Colon

Superior Mesenteric Artery

supplies from cecum to first 2/3 of transverse colon

Inferior Mesenteric Artery

supplies from distal 1/3 of transverse colon to sigmoid colon