Module 9: The Digestive System

Chapter 25 The Digestive System

gastroenterology

Study of the digestive tract and the diagnosis and treatment of its disorders

digestive system

Organ system that processes food, extracts nutrients, and eliminates residue

ingestion

Intake of food

digestion

Mechanical and chemical breakdown of food into a form usable by the body

absorption

Uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

compaction

Absorbing water and consolidating the indigestible residue into feces

defecation (excretion)

Elimination of undigested material (feces)

mechanical digestion

The physical breakdown of food into smaller particles; Cutting and grinding action of the teeth; Churning action of stomach and small intestines

chemical digestion

A series of hydrolysis reactions that breaks dietary macromolecules into their individual monomers; Carried out by digestive enzymes produced by salivary glands, stomach, pancreas, and small intestine

monosaccharides (glucose)

polysaccharides (Carbs) into

amino acids

proteins into

monoglycerides,fatty acids

fats (lipids) into

nucleotides

nucleic acids into

digestive tract (alimentary canal)

30 ft long muscular tube extending from mouth to anus; Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus

gastrointestinal (GI) tract

Stomach and intestines

accessory organs

Teeth, tongue, salivary glands, liver, gallbladder, and pancreas

mucosa

layer of GI tract that contains Epithelium; Lamina propria; Muscularis mucosae

submucosa

layer of GI tract that contains Blood and lymphatic vessels, nerve plexus, glands

muscularis externa

layer of GI tract that contains Inner circular layer; Outer longitudinal layer

serosa

layer of GI tract that contains Areolar tissue or mesothelium

enteric plexus

Nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow

submucosal plexus

Controls glandular secretion of mucosa; Controls movement (contractions) of muscularis mucosae

myenteric plexus

Parasympathetic ganglia and nerve fibers between the two layers of muscularis externa; Controls peristalsis; Contractions of muscularis externa

mesentery

Connective tissue sheet that suspends stomach and intestines from abdominal wall

peritoneum

A serous membrane that lines the peritoneal cavity of the abdomen and covers the mesenteries and viscera

dorsal mesentery

Suspends GI tract and forms serosa (visceral peritoneum) of stomach and intestines

ventral mesentery

Forms lesser and greater omentum; Lacy layer of connective tissue that contains lymph nodes, lymphatic vessels, blood vessels

lesser omentum

Attaches stomach to liver

greater omentum

Covers small intestines like an apron

short (myenteric) reflexes

Stretch or chemical simulations acts through myenteric plexus; Stimulates peristaltic contraction of swallowing

long (vagovagal) reflexes

Parasympathetic stimulation of digestive motility and secretion

functions of the mouth

Ingestion, taste, mechanical digestion, chemical digestion, swallowing, speech, and respiration

stratified squamous

what epithelium lines mouth

vestibule

Space between teeth and cheeks

lips (labia)

Divided into 2 parts

mustache area

Cutaneous area of lip

lipstick area

Red (vermillion area) of lip

tongue

A sensitive organ that is a muscular manipulator of food

palate

Separated the oral cavity from the nasal cavity

hard (bony) palate

Aids in holding and manipulating food

soft palate

Posterior to hard palate

dentition

The teeth

masticate

Chewing

crown

Portion above the gums

periodontal ligament

Anchors teeth into alveoli process; Gomphosis joint (the tooth in the alveolar process)

dentin

Hard yellowish tissue that makes up most of tooth

mastication/chewing

Break foods into smaller pieces to be swallowed

functions of saliva

Moistens the mouth, begins starch and fat digestion, cleanse teeth, inhibit bacteria

salivary amylase

Enzyme that begins starch digestion in the mouth

lingual lipase

Enzyme that digests after it reaches the stomach (activated by stomach acid)

mucus

Binds and lubricates a mass of food and aids in swallowing

lysozyme

An enzyme that kills bacteria

immunoglobulin A (lgA)

An antibody that inhibits bacterial growth

saliva

what has a pH of 6.8-70

parotid,submandibular,sublingual glands

what are the 3 pairs of Extrinsic (major) Salivary Glands

mucous

What do mucous cells secrete

amylase

What do serous cells secrete

1-1.5

Extrinsic salivary glands secrete about #-# L of saliva

bolus

What is it called when mucus in the saliva binds food particles into a soft, slipper easily mass? (ball of food)

esophagus

straight muscular tube 25-30 cm long through esophageal hiatus in diaphragm

lower esophageal sphincter (LES)

Food pauses here because of constriction

mucosa

what has Nonkeratinezed stratified squamous

submucosa

what Contains esophageal glands which secrete mucus

muscularis externa

Skeletal muscle in upper and transcends to smooth in bottom

adventitia

The esophagus is covered in ______

swallowing/deglutition

A complex action involving over 22 muscles in the mouth, pharynx, and esophagus

oral (buccal) phase

What swallowing stage is when tongue collects food, presses it against palate forming bolus, and pushes it posteriorly

pharyngeal phase

What swallowing stage is when it prevents food and drink from reentering mouth or entering the nasal cavity

esophageal phase

Phase-peristalsis

stomach

A muscular sac in upper left abdominal cavity immediately inferior to the diaphragm

main stomach functions

Liquifies food, acts a food storage organ

chyme

acidic, soupy mixture of semi-digested food that passes on to the small intestine; stomach makes this (liquified bolus)

outer longitudinal,middle circular,inner oblique layers

what are the 3 layers of the muscularis externa

simple columnar

what epithelium layer of the stomach wall does mucosa have

regenerative (stem) cells

Divide rapidly and produce continual supply of new cells to replace cells that die

parietal cells

Secrete HCl acid and intrinsic factor

pepsinogen,lipase

Chief cells secrete:

hormone and paracrine messengers

Enteroendocrine cells secrete _______ that regulate digestion

gastrin

G cell produce

intrinsic factor (parietal cells)

Essential for B12 absorption by the small intestine

hemoglobin synthesis

What is B12 necessary for

pernicious anemia

Lack of B12 can cause

pepsin

Protein digestion; Secreted as pepsinogen (inactive form) then HCl converts it to

gastric and lingual lipse

Both play a minor role in digesting dietary fats

gastric motility

It takes 4 hours to empty from stomach

cephalic phase

What phase is when the vagus nerve stimulates gastric secretion and motility just with sight, smell, taste, or thought of food

gastric phase

Activated by presence of food or semidigested protein

Ach,histamine,gastrin

Gastric secretion stimulated mainly by what 3 chemicals

intestinal phase

what phase is when the Duodenum regulates gastric activity through hormones and nervous reflexes

hilum

Irregular opening between quadrate and caudate lobes

gallbladder

Adheres to a depression on the inferior surface of the liver, between right and quadrate lobes

hepatic lobules

Tiny cylinders that fill the interior of the liver

right and left hepatic ducts

Collect bile from all bile ductules of liver lobes

common hepatic duct

right  and left hepatic ducts unite to form the ______ that leaves the liver

bile duct

Formed from union of cystic and common hepatic ducts; descends through lesser omentum toward the duodenum

cystic duct

Coming from gallbladder joins common hepatic duct

gallbladder

Pear shaped sac on underside of liver that stores and concentrates bile

bile

Yellow-green fluid secreted by liver containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids

bilirubin

Principal bile pigment from the decomposition of hemoglobin

urobilinogen

bacteria in large intestine metabolize bilirubin to