Digestive System LAB

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Whats in it?

Alimentary Canal/Gastrointestinal tract

hollow tube from mouth to anus

various accessory organs or glands empty secretions here.

Has 4 layers/tunics: (inner to outer)

mucosa: epithelium, lamina propia, muscularis mucosae. Absorbs and secrete

submucosa: vascular supply for mucosa, protection

muscularis externa: longitudinal muscle, circular muscle. Churning, mixing, propulsion of food

serosa/adventitia: epithelium. Protection

Accessory organs (secrete products to alimentary canal)

teeth

salivary glands

parotid gland: secrete serous

submandibular: mucin and serous components

sublingual : mixed gland makes most mucin

Saliva: has mucin (glycoprotein) creates bolus

gallbladder

when there is no digestive activity, the gallbladder sucks up the bile through cystic duct. When bile is needed its released.

liver

largest gland in body

four lobes, suspended by falciform ligament

produces bile (fat emulsifier), leaves through common hepatic duct and enters duodenum through bile duct

important in inital processing of nutrient rich blood draining digestive organs.

lobules: structural and functional units exagonal consisting of hepatocytes (liver cells). At each 6 corner of lobule is a protal triad which contains portal arteriole, portal venule, and bile duct. Between each cell there is a sinusoid

stellate/hepatic macrophage: phagocytic cells that line sinusoid and remove debris such as bacteria from blood as it goes past while hepatocytes pick up oxygen and nutrients.

Sinusoid empty to central vein and blood drains from liver via hepatic veins. blood filled space that drain into central vein.

acinar cell

pancreas

horizonal across posterior ab wall from spleen to duodenum.

retroperitoneal organ

Both endocrine (insulin/glucagon) and exocrine function of hydrolytic enzymes made by acinar cells which secrete to duodenum through pancreatic duct.

Pancreatic juice: very alkaline, concentration of bicarbonate ion (HCO3-). It neutralizes chyme when entering the duodenum from stomach.

Oral Cavity

Palate: roof of mouth. Hard palate (palatine process of maxillae/palatine bones. Soft palate (fibromuscular no bone)

Uvula: fingerlike projection of soft palate

Tongue: has mylohoid muscle. Attaches to hyoid bone, mandible, styloid process, pharynx

lingual frenulum: secure inferior midline of tongue to floor of mouth

oral vestibule: area between teeth and cheek

oral cavity proper: space within teeth and gums

Palatine tonsil: mass of lymphoid tissue

Palatoglossal arch:

lingual tonsil: lymphoid tissue, part of defense system

tonsilitis: inflammed tonsil blocking entrance to pharnyx making swallowing hard.

Salivary amylase: enzyme that breaks down starch

Pharynx

nasopharynx

oropharynx

largyngopharnx

walls have two layers of skeletal muscle:

inner layer of longitudinal muscle

outer layer of circular constrictor muscles.

Reason is to initiate wavelike contractions that move food into esophagus

mucosa of oro and laryngo have protected squamous epithelium

Esophagus (gullet)

pharynx to diaphagm to gastroesophageal sphincter in superior stomach.

25 cm

food passage by way of peristalsis (wavelike movement)

gastroesophageal sphincter: slight thickening of smooth muscle layer between esophagus and stomach. Controls food passage to stomach

Stomach

mesentary: double layer of peritoneum from digestive organs to body wall

greater omentum: extends from greater curvature of stomach to most of abdominal organs

lesser omentum: liver to lesser curvature of stomach

contains third layer of smooth muscle in muscularis externa allowing it to churn, mix, and pummel food.

Gastric glands: secrete hydrochloric acid and hydrolytic enzymes

Mucosal glands: secrete viscous mucus to prevent stomach from being digested from proteolytic enzymes.

MOST DIGESTION HAPPENS IN PYLORIC PART OF STOMACH

Chyme: creamy mass of food after being in stomach, goes through pyloric sphincter to small intestine

Parts of stomach: Cardial part, fundus, body, pyloric part

Small intestine

20 feet, 6 to 7 meters

pyloric sphincter to ileocecal valve

suspended by mesentary

3 divisions:

duodenum: pyloric sphincter and curves around head of pancreas retroperitoneal position.

intestinal crypts: invaginated area that produces intestinal juice

ileum: terminal portion, joins large intestine at ileocecal valve. Inferior and right in ab cavity, mostly in hypogastric region

jejunum: continues with duodenum, occupies umbilical region of ab cavity

surface area of mucosa:

microvilli: microscopic projections of surface plasma membrane of columnar epithelial

villi: fingerlike projection of mucosa tunic giving velvety appearance

circular folds: deep folds of mucosa and submucosal layers that force chyme to spiral though intestine. Mixing it and slowing progress. Decreases in size and frequency

Peyer's patches: lymphoid nodules

Large Intestine

ileocecal valve to anus

Subdivisions:

cecum

appendix: hangs from cecum. Generally twisted, ideal location for bacteria to multiply

colon: ascending colon, right colic (hepatic) flexure, transverse colon, left colic (splenic) flexure, decending colon, sigmoid colon. CONSIDERED RETROPERITONIAL (except sigmoid and transverse)

rectum,

anal canal: internal anal sphincter (smooth muscle) external anal (skeletal)

longitudinal muscle layer of muscularis externa is reduced to three longitudinal muscle bands called teniae coli, cause wall to pucker into small pocketlike sacs called haustra

Goblet cells: mucus is produced and secreted by them.

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Role/Processes

Role of Digestive System

provide body w/nutrients, water, electrolytes.

Organs ingest/digest food,absorb, eliminate undigested as feces

Digestion

where ingested food is broken to smaller molecules to be available for cells. Then goes to absorption

In small intestine

2 enzymes:

brush border enzymes: hydrolytic enzyme in microvilli of columnar epithelium cells

enzymes made by pancreas and ducted in duodenum via main pancreatic duct.

Bile from liver enters duodenum through bile duct .

At Duodenum ducts join to form hepatopancreatic ampulla and empty product to duodenal lumen through major duodenal papilla, an orifice controlled by muscular valve called hepatopancreatic sphincter.

Absorption

Digested end products pass through epithelial cells lining the tract into the blood for distribution of body cells.

Large intestine

consolidates and propels unusable fecal matter toward anus and eliminate it from body

provides a site where intestinal bacteria manufacture vitamin b and k

reclaim most of water from ndigested food, conserving body water

Movement of bile

made by hepatocytes in liver.

flows through tiny canals called bile canaliculi which run retween adjacent cells toward bile duct branches in triad regions where it leaves liver.

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Diseases

Cirrosis: when liver is severely damaged and becomes hard/fibrous

hepatitis: inflammation of liver

A blocked common hepatic or bile duct:

Jaundice: bile cant enter small intestine, accumulates, and backs up in liver. Causes pressure on liver cells and bile enters bloodstream. As it circulates tissues become yellow or jaundiced.