Bio 65: Ch. 24 Digestive System

ingestion

intake of food

digestion

mechanical and chemical breakdown

absorption

uptake of nutrients

compaction

absorption of water

consolidation of indigestible residue

defaction

elimination of feces

alimentary canal

tube from mouth to anus

gastrointestinal (GI) tract

stomach and intestines

accessory organs

liver, pancreas, gallbladder

mucosa

deepest

epithelial tissue layer

lamina propria

muscularis mucosae

lamina propria

loose connective tissue

muscularis mucosae

smooth muscle

submucosa

2nd deepest layer

loose connective tissue with vessels and nerves

muscularis externa

3rd deepest layer

smooth muscle for propulsion and mixing

inner circular layer and outer longitudinal layer

serosa

superficial layer

areolar tissue topped with simple squamous mesothelium

enteric nervous system (ENS)

* Is the nervous network to esophagus, stomach, intestines containing multiple parasympathetic nerve fibers


* 2 plexuses

2 plexuses of the ENS

submucosal and mysenteric

foregut

esophageal arteries

celiac trunk

midgut

superior mesenteric artery

hindgut

inferior mesenteric artery

mesenteries

connective tissue sheets holding abdominal viscera in place

posterior and anterior mesentery

posterior and anterior mesentary

2 layered membranes that hang freely or connect organs together or to abdominal wall

lesser omentum

extends from lesser curvature of stomach to liver

greater omentum

hangs down like an apron from stomach’s greater cirvature

lesocolon

mesentery of the colon

the mouth

aka oral (buccal cavity)

labial frenulum

median fold attaching lip to gum

vestibule

space just inside lips and cheeks

palate

hard (bony) and soft

body of tongue

anterior 2/3

root of tongue

posterior 1/3

lingual frenulum

attachment to floor of mouth

“tongue-tied”

teeth

also referred to as dentition

mastication

chewing of food

incisors

slicers

canines

puncture and shred

premolars

crush and grind

deciduous teeth

20

permanent teeth

32

a tooth

crown, neck, root

embedded in mandible or maxilla

alevolus

socket

gingiva

surrounds neck of toothe

enamel

covers crown of tooth

internal structures

dentin

pulp cavity, root canal

spaces for nerves and vessels

main salivary glands

parotid, submandibular, sublingual

parotid salivary gland

near ear

* duct opens at 2nd upper molar

submandibular salivary gland

under jaw

* duct opens at lower central incisors

sublingual salivary gland

under tongue

* several duct openings under tongue

oropharynx and laryngopharynx

pass food

* walls contain skeletal muscle that we control for swallowing

esophagus

posterior to trachea

* starts behind larynx and ends at lower esophageal sphincter located at the cardiac orifice to stomach

deglutition

act of swallowing coordinated by our medulla oblongata in the brain stem

external anatomy of stomach

lesser and greater curvature

pyloric part of stomach

antrum, pyloric canal, pyloric sphincter

gastric rugae interally

longitudinal folds in empty stomach

muscous cells

secrete mucus

regenerative (stem) cells

makes new cells

parietal cells

HCl, intrinsic factor (helps with vitamin B12 absorption)

chief cells

pepsinogen (enzyme that breaks down proteins)

enteroendocrine cells

digestive hormones

mucous coat

for protection

thick and highly alkaline (basic) to counteract the stomach fluidti

tight junctions

between epithelial cells

precent seepage of acidic gastric juice

small intestine: duodenum

first 25 cm of SI

contains circular folds to increase surface area for absorption

major duodenal papilla

for bile and pancreatic duct secretion

minor duodenal papilla

for accessory pancreatic duct secretion

small intestine: jejunum

region of SI following the duodenum

lies mostly within umbilical region

most digestion and absorption occur here

small intestine: ileum

last portion of SI

sparse circular folds

contains lymphatic nodules called peyer’s patch

enterocytes

each have tiny microvilli projections to increase absorption

goblet cells

secrete mucus

lacteals

lymphatics for lipid absorption

intestinal crypts

goblet cells and enterocytes

paneth cells

paneth cells

enteroendocrine cells in crypts

large intestine (colon)

cecum (pouch)

cecum

first part of LI

ileum attaches to cecum at the ileocecal valve

appendix

a blind tube that contains lymphatic tissue

ascending colon

on right side of the body

right colic flexure

bend in LI between ascending and transverse colon

transverse colon

runs right to left horizontallyl

left colic flexure

bend in LI between transverse and descending colonde

descending colon

on left side of body

sigmoid colon

last portion

S-shaped

rectum

transverse rectal folds

holds and retains feces

anal columns

folds

anal sinuses

depressions between folds

internal anal sphincter

smooth muscle

involuntary

external anal sphincter

skeletal muscle

voluntary

large intestine epithelium

mostly simple columnar with many goblet cells

liver

body’s largest gland

digestive function is bile production

makes bilirubin

bilirubin

decomposition of hemoglobin

liver lobes

right, left, quadrate, and caudate

falciform ligament

separates right lobe from left lobe

porta hepatis

area between quadrate and caudate lobes

round ligament

remnant of umbilical vein

hepatic lobules

small cylinders with central vein with radiating plates of hepatosytes

hepatic sinusoids

leaky capillaries

stellate macrophages

clean blood running through sinusoids

hepatic portal vein

brings nutrient-rich blood from veins of GI tract to liver

hepatic artery

brings arterial blood

aorta → celiac trunk → common hepatic artery → hepatic artery proper → hepatic artery

hepatic veins

exit from top of liver and empty into inferior vena cava

gallbladder

sac on underside of liver

stores and concentrates biles

has fundus, cervix

cystic duct

from gallbladder merges with common hepatic duct