IU ANAT-A 225 Block 5

Gastrointestinal (GI) tract

tube that extends from mouth (oral cavity) to anal canal, includes: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anal canal

peristalsis

waves of contraction, pushes food further along

Accessory Digestive Organs

not part of GI tract, but assist with digestion, tongue, teeth, salivary glands, liver, gallbladder, pancreas

Mechanical digestion

physically breaking down food, teeth chewing, stomach muscle churning

Chemical digestion

salivary glands/saliva uses enzymes to break down food

Absorption

water and food molecules pass through the intestines and move into other structures

GI lymphatics (lacteals)

absorb dietary lipids and lipid-soluble vitamins

Blood vessels

absorb all other digested nutrients

parietal peritoneum

outer lining of abdominopelvic cavity

visceral peritoneum

inner lining of abdominopelvic cavity

peritoneal cavity

spaces in abdominopelvic cavity

Oral cavity

continuous posteriorly with oropharynx, nonkeratinized stratified squamous epithelium, includes palate, teeth, tongue, salivary glands

hard palate

anterior 2/3 of palate, bony, palatine bone and maxilla

soft palate

posterior 1/3 of palate, formed from skeletal muscle, contains uvula

uvula

rises to close off the nasopharynx when we swallow

permanent teeth

32, 2 incisors, 1 canine, 2 premolars, 3 molars on each side

deciduous (baby) teeth

2 incisors, 1 canine, 2 molars on each side

Tongue

skeletal muscle covered with mostly nonkeratinized stratified squamous epithelium, perceives taste, mechanical digestion

tongue innervation

motor: CN XII - Hypoglossal, taste: CN VII - facial and CN IX - glossopharyngeal, sensation: CN V - trigeminal, and CN IX - glossopharyngeal

salivary glands

three pairs, parotid, submandibular, sublingual, secrete saliva

parotid gland

largest of the salivary glands and are located on each side of the head anterior and inferior to the ear, partially overlying the masseter muscle

submandibular gland

2

sublingual gland

3

functions of saliva

dissolves food molecules for taste, moistens food, cleanses mouth, chemical digestions of carbs, lysozyme and antibodies in saliva inhibit bacterial growth in mouth, innervated by CN IX - glossopharyngeal nerve

Pharynx

throat, skeletal muscle, skeletal muscle tube that connects nasal cavity and mouth to larynx and esophagus, skeletal muscle propels food and drink to esophagus or air to larynx, only oropharynx and laryngopharynx conduct both food and air

Mucosa

innermost tunic, esophagus: nonkeratinized stratified squamous, stomach to anal canal: simple columnar epithelium

lamina propria

areolar connective tissue

muscularis mucosae

thin layer of smooth muscle

submucosa

connective tissue, contains major blood vessels

muscularis

2 layers of smooth muscle, inner circular and outer longitudinal, esophagus has two layers of skeletal and smooth muscle, and the stomach has 3 layers of smooth muscle, responsible for peristalsis

Serosa

outermost layer, visceral peritoneum + areolar connective tissue

adventitia

outermost layer, areolar connective tissue only

esophagus

propels food to the stomach, muscular tube that connects the pharynx to the stomach

esophagus mucosa

nonkeratinized stratified squamous epithelium (histology)

esophagus muscularis

2 layers of muscle, upper 1/3: skeletal muscle, middle 1/3: skeletal + smooth muscle, lower 1/3: smooth muscle only

reflux esophagitis (heartburn)

stomach contents reflux into esophagus, causing burning, risk factors: overweight, smoking, large meals before bedtime

vestibule

space between the teeth and the lips or cheeks

palatine tonsils

paired lateral masses of lymphatic nodules at the border between the oral cavity and the oropharynx

vallate papillae

form an inverted V a the boundary between the anterior two-thirds and posterior one-third of the surface of the tongue

crown

extending into the oral cavity, covered by enamel

neck

narrow, slightly constricted region below the crown, in contact with the gums that cover the alveolar processes of the mandible and maxillae

root

one or more to anchor the tooth into itsalveolus

dentin

forms the bulk of the tooth; it is a hard, yellowish, calcified substance

enamel

the hardest substance in the body and is composed largely of inorganic salts, the enamel covers the dentin of the crown

cementum

bonelike substance which surrounds the dentin of the root and helps anchor the tooth

pulp

connective tissue with blood vessels and nerves found in pulp cavity

pulp cavity

holds pulp

root canal

narrow core of each root

parotid duct

passes over the masseter muscle, pierces the buccinator muscle and enters into the vestibule of the oral cavity opposite the second upper molar tooth

periodontal ligaments

composed of dense regular connective tissue and run between the bone of the alveolus and the cementum to anchor the tooth

submandibular gland

located along the medial aspects of the mandible, each with superficial portion which is continuous posteriorly around the mylohyoid muscle with a larger deep portion

sublingual glands

on the anterior floor of the mouth, deep to the oral cavity mucosa

stomach

joins the esophagus and small intestine, shape and position are modified by its volume changes and surrounding structures

greater curvature

left and inferior border of stomach, attached to the greater omentum

lesser curvature

left and inferior border of the stomach, attached to the lesser omentum

pyloric sphincter

thick ring of smooth muscle in the pyloric orifice

cardiac

area immediately surrounding the cardiac orifice

body

the main, central portion of the stomach

fundus

bulges superior to and to the left of the cardiac orifice

pylorus

tapers toward the pyloric sphincter at the distal end of the stomach

gastric folds

branching folds which run longitudinally, these stretch when stomach is full

stomach mucosa

simple columnar epithelium, mucosa contains gastric pits, branching off gastric pits are gastric glands

stomach muscularis

3 layers of smooth muscle, not 2, has innermost oblique layer, inner circular, and outer longitudinal

small intestine

form pyloric sphincter to ileocecal valve to join the large intestine, duodenum, jejunum, and ileum. Finishes chemical digestion, absorbs 90% of nutrients

duodenum

first and shortest segment of small intestine, behind the parietal peritoneum, receives chyme from stomach, receives bile from liver and pancreatic enzymes through duodenal papilla

jejunum

second segment of small intestine, 2/5 of the small intestine, huge surface area for absorption

ileum

final 3/5 of the small intestine, loosely attached to the mesentery, connects cecum to large intestine, few folds but contains more MALT

small intestine mucosa

simple columnar epithelium with goblet cells and microvilli, with lacteals

small intestine circular folds

folds of mucosa and submucosa, increase surface area for nutrient absorption, slow down chyme and allow it to mix with intestinal juices, allowing time for full nutrient absorption

villi

folds on small intestine mucosa only, increase surface area, provide great distance for material to be ingested and absorbed, in the center of each villus are blood vessels and a lacteal

major duodenal papilla

helps bring bile and pancreatic enzymes into the duodenum

large intestine

extends form the end of the ileum to the anus, absorption of water and electrolytes, storage of undigested material until it can be expelled

cecum

connects to ileum, vermiform appendix attaches to this, lower right side of the abdominal cavity as, short wide pouch

ascending colon

right side of body, ascends along the posterior abdominal wall from the cecum to near the liver

transverse colon

runs from right to left side of body

greater omentum

hangs inferiorly from the transverse colon in front of the small intestine

descending colon

descends along the posterior body wall from near the spleen to the pelvic region

sigmoid colon

as the descending colon enters the pelvis, it curves toward the midline of the body in an S-shape

rectum

begins where the sigmoid colon passes beneath the parietal peritoneum and runs inferiorly along the sacrum toward the pelvic diaphragm

anal canal

last and shortest segment of large intestine, begins at the pelvic diaphragm and ends at the anus

anal sphincter

anal canal surrounded by internal and external muscles

large intestine mucosa

simple columnar epithelium with goblet cells

large intestine muscularis

2 layers of smooth muscle, outer longitudinal layer consists of teniae coli, and haustra

teniae coli

longitudinal bundles of smooth muscle fibers forming three distinct bands

haustra

large intestine wall tends to form a series of sac-like structures

omental appendices

hanging from the haustra are folds of peritoneum filled with adipose tissue

liver

produces and secretes bile, processes the products of digestion, stores glycogen, largest internal gland and is situated under the diaphragm in the upper right part of the abdominal cavity

right lobe

left lobe

quadrate lobe

caudate lobe

gallbladder

bile produced by the liver is carried by ducts to here where it is stored and concentrated until needed, by the inferior surface of the liver at the medial border of the right lobe

common hepatic duct

receives smaller ducts from the lobes of the liver and is joined by a duct from the gallbladder

cystic duct

duct from the gallbladder, carries bile from the common hepatic duct to the gallbladder, or from the gallbladder to the common bile duct

common bile duct

runs from the junction of the common hepatic duct and cystic duct to the duodenal wall, it is joined by the main pancreatic duct to enter the duodenum at the major duodenal papilla

pancreas

located behind the stomach and runs from the inner curve of the duodenum to the vicinity of the spleen, acinar cells secrete pancreatic juice

pancreatic duct

runs the length of the pancreas to join the common bile duct at the duodenum, pancreatic juice leaves via this

celiac trunk

supplies abdominal digestive organs

left gastric artery

branch of celiac trunk

common hepatic artery

branch of celiac trunk