Digestive System

muscular tube that winds from the mouth to the anus

teeth, tongue and salivary glands

gallbladder, liver and pancreas

first step of the digestive process

taking food into the mouth

second step of the digestive process

movement of food through the GI tract

third step of the digestive process

mechanical and chemical processes that break down food

fourth step of the digestive process

movement of food into blood and lymph capillaries

fifth step of the digestive process

elimination of waste materials

ripple-like wave of muscular contractions that move food along the GI tract

churning and mixing to help disperse material and combine it with digestive secretions

innermost layer of the wall of the alimentary canal

consists of three sublayers: epithelium, lamina propria and muscularis mucosae

top layer of the mucosa

consisting of squamous columnar epithelium

different functions depending on the location

second layer of the mucosa

loose areolar connective tissue (blood vessels)

capillaries nourish epithelium and absorb digested nutrients

bottom layer of the mucosa

thin layer of smooth muscle that produces local movements of the mucosa

layer of connective tissue surrounding the mucosa containing major blood and lymphatic vessels, nerves

elastic fibers enable canal to return to original shape after passage of food

two layers of smooth muscle surrounding the submucosa

inner circular and outer longitudinal - responsible for peristalsis

esophagus has a mixture of smooth and skeletal muscle

stomach contains three layers of smooth muscle

outer layer of the alimentary canal consisting of simple squamous epithelium

areolar connective tissue (blood vessels)

also called adventitia or visceral peritoneum

humans normally have 32 permanent

incisors, canines, premolars, molars

nipping off pieces of food (8)

front teeth

tearing and piercing (4)

after incisors

grinding of food

20 total at the back of the mouth

type of salivary gland consisting of many small glands that keep oral cavity moist

type of salivary gland that lie external to mouth but connect through ducts

active when feeding

swallowed food is passed posteriorly into oropharynx and laryngopharynx

makes use of pharyngeal constrictor skeletal muscles

first phase of swallowing

bolus pushed by tongue against hard palate and to oropharynx

second phase of swallowing

soft palate and uvula close off nasopharynx

epiglottis covers laryngeal opening

final phase of swallowing

peristalsis pushes bolus towards stomach

muscular tube that propels food to stomach

passes through esophageal hiatus in diaphragm

contains the four layers of the GI tract

epithelium is stratified squamous epithelium

highly folded when empty

lots of mucous glands that are triggered by food bolus

muscularis changes from skeletal to smooth as it approaches stomach

prevents stomach acid from re-entering the esophagus

temporary storage organ in which food is churned into chyme

divided into various regions

internal surface contains numerous longitudinal folds called rugae

surface of the mucosa is columnar epithelia

extending down into lamina propria are gastric glands

produce very acidic solution with digestive enzymes (gastic juice)

lots of mucous

epithelial cells have tight junctions

damaged cells replaced quickly

craterlike erosion of the mucosa in any part of the alimentary canal exposed to stomach secretions

about 98% occur in pyloric region of stomach (gastric ulcer) or first part of duodenum (duodenal ulcers)

stomach contents leaked into the peritoneal cavity

longest part of alimentary canal

site of most enzymatic digestion and nearly all absorption

large surface area

food spends at least 12 hours here where chemical digestion takes place

3 regions

first section of the small intestine emerging from the stomach

25 cm in length

where bile and pancreatic secretions enter the intestine

middle of the small intestine

1m long

primary region for chemical digestion and nutrient absorption

last region of the small intestine that empties into the large intestine

sphincter controls material entering into large intestine

responsible for absorption of vitamin B12 and bile salts

patches of lymph tissue

internally get circular folds with villi increasing the surface area of intestinal lining

each contain an arteriole, venule, capillaries and lacteal

microscopic microvilli are found on the surface of each villus

invaginations into mucosa found between villi

secrete intestinal juice, digestive enzymes, hormones, mucous, etc.

diseases associated with these glands are colorectal caner, Crohn's diseas and cryptitis

1.5m extending from the ileum to anus

frames the small intestine on three sides

consists of the cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, rectosigmoid colon and rectum

three separate longitudinal bands of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons

thickenings of the muscularis

saccules in the colon that give it its segmented appearance

series of pouches caused by the contraction of teniae coli

blockage traps bacteria in lumen of appendix

begins to swell with mucous and leads to an infection

refers to presence of small pockets (diverticula) in large intestine

in some cases, spasms, cramping, diarrhea, constipation

inflamed diverticula become infected and perforate

portion of the large intestine

no teniae coli

well developed muscularis to generate strong contractions

last 3 cm of the large intestine

internal sphincter consists of smooth muscle

external sphincter consists of skeletal muscle

stretched and inflamed veins that bulge into the lumen of the anal canal

can be caused by straining to defecate or delivering a baby

accessory organ of digestion

liver is largest gland of body

comprised of four incompletely separated lobes

falciform ligament completely divides right from left lobe

digestive function is to produce bile

bile is then stored in gallbladder

dumped into duodenum via bile duct

chronic inflammation of the liver

usually the result of hepatitis or alcoholism

main cell types of liver damaged, replaced by scar tissue

only effective treatment are liver transplants with a good survival rate but few donors available

inflammation of the liver

often due to viral infection

six different viruses known so far (A-F)

type A from contaminated food, water and feces

type B from blood transfusions, contaminated needles and sexually transmitted fluids

if there is too much cholesterol for bile to break down, it can become crystalized

cause substantial pain if they block cystic duct

accessory organ in digestion

produce most of enzymes that digest food in small intestine (pancreatic juice secreted through two ducts)

also lots of bicarbonate to neutralize the acid from stomach

main pancreatic duct merges with common bile duct

accessory duct enters duodenum proximally

pancreatic enzymes activated in pancreas instead of small intestine

abdominal pain, nausea, vomiting

acute lasts a few days and is normally caused by gallstones

chronic persists over many years and is often related to high consumption of alcohol

dangerous to screen for, yet deadly if ignored

pancreas is very sensitive and biopsies can lead to serious complications

cancer is usually detected too late

five-year survival rate of less than 5%

emphasis on earlier detection