The Digestion System and Body Metabolism

digestion

breakdown of ingested food and absorption of nutrients into the blood

metabolism

production of cellular energy and constructive and degradative cellular activities

alimentary canal and accessory digestive organs

two main groups of organs of the digestive system

accessory glands

mouth (oral cavity) and tongue

mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus

organs of the alimentary canal

lips

aka: labia

protect the anterior opening of the mouth

-number 2

cheeks

form the lateral walls of the mouth

hard palate

forms the anterior roof of the mouth

soft palate

forms the posterior roof of the mouth

uvula

fleshy projection of the soft palate in the mouth

vestible

space between lips externally and teeth and gums internally of the mouth

oral cavity

area contained by the teeth

tongue

attached at hyoid and styloid processes of the skill, and by the lingual frenulum of the mouth

-number 4

tongue tied

children born with extremely short lingual frenulum are referred to as this, due to movement of the tongue being restricted

-can be corrected by surgery or cut of frenulum

lingual frenulum

fold of mucus membrane that secures the tongue to floor of the mouth and limits its posterior movement

tonsils

in the mouth, along with other lymphatic tissue help to provide in body’s defense system

-palatine (posterior) and lingual (anterior)

mastication

chewing of food

mastication, mixing masticated food with saliva, initiation of swallowing by the tongue, and allowing for sense of taste

processes of the mouth

nasopharynx, oropharynx, laryngopharnyx

parts of pharynx

nasopharynx

subdivision of pharynx

-not part of the digestive system, passes food posteriorly from mouth into oropharynx

-green area

oropharynx

subdivision of pharynx

-posterior to oral cavity

-yellow area

laryngopharynx

subdivision of pharynx

-below the oropharynx and connected to the esophagus

-blue area

passageway for air and food, moves food to the esophagus, and moves food by peristalsis

function of the pharynx

longitudinal and circular

two skeletal muscle layers of the pharynx

inner layer

longitudinal muscle layer of pharynx

outer layer

circular muscle layer of pharynx

esophagus

aka: gullet

runs from pharynx to stomach through the diaphragm and conducts food by peristalsis

-passageway for food only

mucosa, submucosa, muscularis externa, and serosa

layers of alimentary canal organs (from esophagus to large intestine)

mucosa

innermost layer of alimentary canal organs

-moist, epithelium membrane with small amount of connective tissue, small smooth muscle layer

-lines the cavity (or lumen) of the organ

submucosa

second layer of alimentary canal organs

-just beneath the mucosa

-soft connective tissue with blood vessels, nerve endings, and lymphatics (mucous associated lymphoid tissue and lymphatic vessels)

muscularis externa

third layer of alimentaty canal organs

-smooth muscle that consist of inner circular layer and outer longitudinal layer

serosa

fourth layer of alimentary canal organs

-visceral peritoneum is continuous with the slick slippery parietal peritoneum which lines the abdominopelvic cavity by way of the mesentary

-layer of serous fluid-producing cells

peritonitis

condition in which peritoneum is infected and when the peritoneal membrane sticks together around the infected site

-helps to seal off and localize many intraperitoneal infections providing time for macrophages in the lymphatic tissue to mount an attack

helps regulate the mobility and secretory activity of GI tract organs

function of the layers of alimentary canal organs

myenteric

“intestinal muscle”

stomach

located on the left side of the abdominal cavity, nearly hidden by liver and diaphragm

cardioesophageal sphincter

site where food enters the stomach

cardiac region, fundus, body, and phylorus

regions of the stomach (left side of abdominal cavity)

cardiac region

region of the stomach near the heart

-surrounds the cardioesophageal sphincter through which food enters from the esophagus

fundus

region of the stomach dome-shaped part

body

region of the stomach- the midportion and narrows inferiorly becomes pyloric antrum

phylorus

region of the stomach- funnel-shaped terminal end

pyloric sphincter

where does food empty into the small intestine

rugae

internal folds of the mucosa in the stomach

lesser curvature

concave medial surface of the stomach

greater curvature

convex lateral surface of the stomach

lesser and greater omentum

layers of the peritoneum attached to the stomach

-contains fat to insulate, cushion, and protect abdominal organs- contains macrophages and defensive cells of the immune system

lesser omentum

layer of peritoneum that attaches the liver to the lesser curvature of the stomach (double layer of peritoneum)

greater omentum

layer of peritoneum that attaches the greater curvature to the posterior body wall of the stomach

-drapes downward and covers the abdominal organs

stomach

functions of stomach

organ that acts as a storage tank for food

-food breakdown

-chemical breakdown of protein BEGINS here

-delivers chyme (processed food) to the small intestine

mucous neck cells, gastric glands, chief cells, parietal cells, endocrine cells

specialized mucosa of the stomach

-all simple columnar epithelium

mucous neck cells

specialized mucosa of the stomach that produces a sticky alkaline mucus

-clings to the stomach mucosa and protects the stomach wall from being damaged by acid and digestive enzymes- dotted with millions of deep gastric pits which lead to gastric glands

gastric glands

specialized mucosa of the stomach that secrete gastric juice

-stomach cells produce intrinsic factor, which is a substance needed for absorption of B12 of small intestine

chief cells

specialized mucosa of the stomach that produce protein-digesting enzymes (pepsinogens)

parietal cells

specialized mucosa of the stomach that produce hydrochloric acid

-make stomach contents acidic and activated enzymes ie: conversion of pepsinogens to pepsin

endocrine cells

specialized mucosa of the stomach that produce gastrin (hormone important in digestion)

mucous neck cells

specialized mucosa of the stomach that has an unknown purpose

-thin acidic mucous

gastric pits

what is formed by the folded mucosa of the stomach mucosa

gastric gland region

what regions of the stomach mucosa contains glands and specialized cells

small intestine

body’s major digestive organ and site of nutrient absorption into the blood

-where nearly all food absorption occurs

pyloric sphincter

where does chyme enter the small intestine

small intestine

muscular tube extending from the pyloric sphincter (end of stomach) to the ileocecal valve (where ileum meets large intestines)

-suspended from the posterior abdominal wall by the mesentery

duodenum, jejunum, ileum

subdivisions of the small intestine

pyloric sphincter

“gatekeeper”- controls food from stomach to small intestine and keeps small intestine from being overwhelmed

duodenum

subdivision of small intestine

-attached to the stomach and curves around the head of the pancreas

jejunum

subdivision of the small intestines

-attaches anteriorly to the duodenum

ileum

subdivision of the small intestines

-extends from jejunum to large intestine

-meets the large intestine at the ileocecal valve

chemical digestion in the small intestine

source where enzymes are mixed with chyme (intestinal cells and pancreas)

-bile enters from the gall bladder to the bile duct

villi of the small intestine

fingerlike structures formed by the mucosa of small intestine

-give small intestine more surface area

contains a rich capillary bed and a modified capillary called a lacteal

microvilli, villi, and circular folds

3 structures in small intestines used to increase absorptive surface

microvilli

small projections of the plasma membrane found on absorptive cells of the small intestine

-aka: brush border

-these membrane cells near enzymes (brush border enzymes) that complete the digestion of proteins and carbs

circular folds

aka: plicae circulares

-deep folds of mucosa and submucosa layers of small intestine

large intestine

organ that is larger in diameter but shorter than small intestine and frames the internal abdomen

-runs from ileocecal valve to anus

absorption of water and eliminates indigestible food from body as feces

functions of the large intestine

-does not participate in digestion of food

-goblet cells produce mucus to act as a lubricant (eases passage of feces to the end of the digestive tract)

cecum

structure of the large intestine

-saclike first part of the large intestine

-”D”

appendix

structure of the large intestine

-hangs from the cecum

-accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)

appendicitis

inflammation of appendix, usually because it is twisted and will harbor bacteria that accumulates

colon, rectum, anus

major structures of the large intestine

ascending colon

subdivision of colon

-travels up the right side of the abdominal cavity and makes a turn, the right colic (hepatic) flexure, and travels across the abdominal cavity into the transverse colon

-”C”

transverse colon

subdivision of the colon

-takes a turn at the left colic (or splenic) flexure, and continues down the left side into the descending colon

-”A”

descending colon

subdivision of the colon

-continues down left side and enters the pelvis

-“H”

s-shaped sigmoidal

subdivision of the colon

-along with the rectum and anal canal, lies in the pelvis

-”G”

rectum

major structure of the large intestine

-”E”

anus

major structure of the large intestine

-external body opening

voluntary sphincter- external anal spincter

internal anal sphincter- made of skeletal muscle and involuntary muscle

-”F”

muscularis externa

3rd layer of muscle (obliquely arranged layer) that all 3 chum mix and pummel fold in stomach

haustra

walls formed into pocketlike sacs in large intestine

salivary glands, teeth, pancreas, liver, gall bladder

5 accessory digestive organs

mumps

common childhood disease that is an inflammation of the parotid gland

-hurts to open mouth or chew food

parotid glands, submandibular glands, and sublingual glands

saliva-producing glands

parotid gland

saliva-producing gland located anteriorly to ears

-”1”

submandibular glands

saliva-producing gland that enters secretion into floor of mouth through tiny ducts

-”2”

sublingual glands

saliva-producing gland that enters secretion into floor of mouth through tiny ducts

-”3”

saliva

mixture of mucus and serous fluids that help to form a food bolus

-contains salivary AMYLASE to begin starch digestion

-dissolves chemicals so they can be tasted

teeth

masticates (chews) food

-humans have 2 sets

deciduous

aka: baby or milk teeth- starting to form by 6 months

-20 teeth are fully formed by age two which causes roots of milk teeth to be absorbed between 6-12 years

lower central incisorsf

first teeth to erupt

3rd molars

all teeth but which ones have erupted by end of adolescence

-aka: wisdom teeth (17-25 years old)

-can be sometimes completely absent or do not erupt

permanent teeth

replaces deciduous teeth beginning between the ages of 6 to 12

-full set is 32, but some people do not have wisdom teeth

dentine

what teeth are made up of