Digestive System Test

Alimentary Tract

- GI tract

- food moves through these organs

-Mouth to anus

-Digests food and absorbs fragments

-Mouth, pharynx, esophagus, stomach, small intestine, and large intestine

Accesory digestive organs

-food doesn't move through these organs

-helpers to process

-Teeth, tongue, gallbladder

-Digestive glands, Salivary glands

-Liver

-Pancreas

Digestive Processes

1. Ingestion=eating

2. Propulsion=move food

3. Mechanical breakdown

4. Digestion=break apart molecules

5. Absorption=nutrients into bloodstream

6. Defecation=poop

Segmentation

separates chyme and then pushes it back together, mixing it and providing time for digestion and absorption.

chyme

Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach.

Peritoneum

-Double-layered membrane surrounding the abdominal organs

-Routes for blood vessels, lymphatics, and nerves

-Holds organs in place; stores fat

Mesentary

supportive membrane surrounding internal organs and attaching to the body wall (just small intestine)

-Routes for blood vessels, lymphatics, and nerves

-Holds organs in place; stores fat

Peritonitis

-Inflammation of peritoneum

-Causes by e.g., piercing abdominal wound, perforating ulcer, ruptured appendix

-Dangerous and lethal if widespread

-Treated with debris removal and antibiotics

hepatic arteries

carry oxygenated blood from the aorta to the liver

splenic arteries

supplies the spleen

left gastric arteries

Supply the esophagus in the abdomen

inferior mesenteric artery

Supplies arterial blood to the large intestine.

superior mesenteric artery

supplies the small intestine

hepatic portal circulation

-Drains nutrient-rich blood from digestive organs

-Delivers it to the liver for processing

filiform (tongue)

whitish, give the tongue roughness and provide friction; do not contain taste buds

fungiform (tongue)

reddish, scattered over tongue; contain taste buds

Circumvallate (vallate)

-V-shaped row in back of tongue; contain taste buds

-Lingual lipase

-secreted by cells on tongue

-Fat-digesting enzyme functional in stomach

Extrinsic salivary glands

-Produce most saliva; lie outside oral cavity

-Parotid

-Submandibular

-Sublingual

Intrinsic salivary glands

small glands dispersed amid other oral tissues

Function of Saliva

-Cleanses mouth

-Dissolves food chemicals for taste

-Moistens food; compacts into bolus

-Begins breakdown of starch with enzymes - amylase

sublingual: mostly mucous cells =

mucusy saliva

Parotid and Submandibular: mostly serous cells =

watery saliva

Composition of saliva

-97-99.5% water, slightly acidic

-Electrolytes—Na+, K+, Cl-, PO4 2-, HCO3-

-Salivary amylase and lingual lipase

-Mucin

-Metabolic wastes—urea and uric acid

-Lysozyme, IgA, defensins, and a cyanide compound protect against microorganisms

control of salivation

-1500 ml/day

-Intrinsic glands continuously keep mouth moist

-Extrinsic salivary glands activated by parasympathetic nervous system when

Ingested food stimulates chemoreceptors and mechanoreceptors in mouth = salivate!!

Enamel

hardest substance in the body

dentin

boney like material

Periodontal ligament

Holds tooth in the socket

pulp cavity

site of blood vessels and nerves

gingival sulcus

space between the free gingiva and the tooth surface

crown (of tooth)

exposed tooth

root (of tooth)

below the gum line

Dental caries

-cavities

-demineralization of enamel and dentin from bacterial action

Dental plaque

-film of sugar, bacteria, and debris adheres to teeth

-Acid from bacteria dissolves calcium salts

-Proteolytic enzymes digest organic matter

-Prevention: daily flossing and brushing

gingivitis

-Plaque calcifies to form calculus (tartar)

-Calculus disrupts seal between gingiva and teeth

-Anaerobic bacteria infect gums

-infection reversible if calculus removed

Periodontitis

- from neglected gingivitis

- Immune cells attack intruders and body tissues

- Destroy periodontal ligament

- Activate osteoclasts → dissolve bone

- Possible tooth loss

Mastication

-Cheeks and closed lips hold food between teeth

-Tongue mixes food with saliva; compacts food into bolus

-Teeth cut and grind

-Partly voluntary

-Partly reflexive

-Stretch reflexes; pressure receptors in cheeks, gums, tongue

Ingestion

taking in food

mechanical digestion

chewing, mixing, and churning food

propulsion

the force that drives something forward, or forward motion

deglutition

swallowing

chemical digestion

-Process by which enzymes break down food into small molecules that the body can use

-no absorption (except for a fex drugs)

buccal phase

Tongue collects food compacts it and pushes it back to the oropharynx

Pharyngeal-esophageal phase

Involuntary - primarily vagus nerve

Control center in the medulla and lower pons

esophageal hiatus

where the esophagus passes through the diaphragm

Gastroesophageal (cardiac) sphincter

-surrounds cardial orifice

-keeps orifice closed when food is not being swallowed

-mucus cells on both sides of sphincter help protect esophagus from acid reflux

Heartburn and GERD

Stomach acid regurgitates into esophagus

Likely with excess food/drink, extreme obesity, pregnancy, running

cardial part

surrounds the cardial orifice through which food enters the stomach from the esophagus

fundus

Dome-shaped region beneath diaphragm

pyloric sphincter

Controls passage of food from stomach to small intestine

mucosa of stomach

Simple columnar epithelium composed of mucous cells

Dotted with gastric pits → gastric glands

Gastric glands produce gastric juice

gastric gland secretions

Glands in fundus and body produce most gastric juice

Chief cells secrete

pepsinogen and gastric lipase

parietal cell secretion

HCl and intrinsic factor

mucosal barrier of stomach

thick layer of bicarbonate-rich mucus

Slows down acid erosion

Tight junctions between epithelial cells

Prevent juice seeping underneath tissue

Damaged epithelial cells quickly replaced by division of stem cells

Surface cells replaced every 3-6 days

gastritis

Inflammation caused by anything that breaches mucosal barrier

peptic or gastric ulcers

Erosions of stomach wall

Most caused by Helicobacter pylori bacteria

Some by NSAIDs like ibuprofen

only stomach function essential for life

Secretes intrinsic factor for vitamin B12 absorption

B12 needed → mature red blood cells

gastrin hormone

Released by the stomach lining, duodenum and pancreas

Triggered by: mental anticipation of food or stomach stretch.

Stimulates HCl production by the parietal cells

Stimulates motility of the muscularis to churn and move chyme

Phase 1 of Gastric Secretion (making stomach juices)

Cephalic-thinking about food=make more juices

Phase 2 of Gastric Secretion

Gastric-eating food=make more juices

Phase 3 of gastric secretion

Intestinal=food is leaving stomach and juice production slows

small intestine

major organ of digestion and absorption

2-4 m long

haustra

pouches that form in the large intestine when the longitudinal muscles are shorter than the colon

internal anal sphincter

smooth muscle, involuntary

external anal sphincter

skeletal muscle, voluntary

digestive processes in large intestine

Residue remains in large intestine 12-24 hours

No food breakdown except by bacteria

Vitamins (made by bacterial flora), water, and electrolytes (especially Na+ and Cl-) reclaimed

Major functions - propulsion of feces to anus; defecation

Colon not essential for life

defecation

Mass movements force feces toward rectum

Distension (full colon) initiates spinal defecation reflex

Parasympathetic signals

Stimulate contraction of sigmoid colon and rectum

Relax internal anal sphincter

Conscious control allows relaxation of external anal sphincter

Muscles of rectum contract to expel feces

defecation reflex

normal response to the presence of feces in the rectum

digestive recap

Bolus created in mouth

Swallowed and travels down esophagus to stomach (gastroesophageal sphincter)

Mixes with digestive juices in stomach = chyme

Spurted into duodenum (pyloric sphincter)

Liver and pancreas squirt bile and digestive juices into duodenum

Duodenum, Jejunum and Ileum=digestion and absorption of all food stuff/water/etc

7) Peristalsis to large intestine through iliocecal valve

8) Moves through large intestine with water and electrolytes from cecum, to ascending colon, transverse colon, descending colon, sigmoid colon and rectum

9) And finally.... You poop (AKA defecation)

enzyme/digestive recap

Mouth: salivary amylase, lingual lipase

Stomach: HCl, Pepsinogen/Pepsin, lipase

Duodenum: bile, protease, nuclease, lipase, amylase

liver

receives oxygenated blood from the hepatic artery and nutrient-rich deoxygenated blood from the hepatic portal vein.

detoxifies chemicals in the blood from the digestive system

-Releases bile into the duodenum. Bile emulsifies fat.

hepatitis

Usually viral infection, drug toxicity, wild mushroom

cirrhosis

Progressive, chronic inflammation from chronic hepatitis or alcoholism

scarring of liver

gallbladder

stores and concentrates bile, and releases it into the two-way cystic duct when it is needed by the small intestine.

Exocrine function of Pancreas

The pancreas has a head, a body, and a tail.

It delivers pancreatic juice to the duodenum through the pancreatic duct.

Pancreatic juice contains enzymes to break down all food types: amylase, protease, lipase, nuclease