Digestive System Basic Divisions – Digestive tract – Accessory organs: various exocrine glands.

Digestive System

Digestive System

• Basic Divisions

– Digestive tract

– Accessory organs: various exocrine glands

• Digestive Processes

– Ingestion

– Mechanical Processing

– Motility

•Peristalsis

• Digestive Processes

– Ingestion

– Mechanical Processing

– Motility

•Peristalsis

•Segmentation movements

• Digestive Processes, continued

– Chemical digestion

– Secretion

– Absorption

– Excretion and defecation

• Non-Digestive Functions of Digestive Tract

– Immunity

– Storage of iron

• Layers of the digestive tract– Mucosa

• Epithelium• Lamina propria (areolar CT)

• Muscularis mucosae

• Layers of the digestive tract, continued

– Submucosa

• includes the

•submucosal plexus


– Muscularis externa:

responsible for peristalsis and segmentation movements

• longitudinal layer

• circular layer

• myenteric plexus

• Layers of the digestive tract, continued– Serosa (the visceral

peritoneum is an example)• Simple squamous epithelium

• Areolar CT Within peritoneal cavity

only


– Adventitia

• Dense irregular CT Oral cavity, pharynx,

esophagus, rectum

• The Peritoneum

– Parietal p.

– Visceral p.

• The mesenteries

– Mesentery proper

– Mesocolon

– Greater omentum

– Lesser omentum

– Falciform ligament

• Accessory structures of the oral (buccal) cavity– Teeth: will cover in lab– Tongue: read textbook– Salivary glands

• buccal glands• lingual glands

• Oral (buccal) cavity– Salivary Glands

• buccal glands• lingual glands• major salivary glands

– parotid

• Oral (buccal) cavity– Salivary Glands

• buccal glands• lingual glands• major salivary glands

– parotid– sublingual– submandibular

– Structure of salivary glands

• glandular epithelium

• merocrine cells

– Structure of salivary glands

• glandular epithelium

• merocrine cells

• compound tubulo-acinar

– Functions of saliva

• lubrication for swallowing, speaking

• re-mineralizes tooth enamel

• buffer

• antibodies (IgA)

• dissolves food molecules

• some chemical digestion

• Pharynx

– To be discussed with the respiratory system

• Esophagus

– Structural features

• muscular tube about 25 cm long

• posterior to larynx, trachea

• pierces diaphragm through esophageal hiatus

• 2 Esophogeal sphincters:

– upper esophageal sphincter

– lower esophageal sphincter

• Histology highlights

– mucosa

– submucosa: lots of mucous glands

– muscularis externa

– adventitia (no serosa)

• Gastroesophageal Reflux

• Stomach

– Location

• Stomach

– Location: from epigastric and umbilical region

• Stomach

– Location: from epigastric and umbilical region to left hypochondriac regions

• Gross Structural Features– cardiac

region– fundus– body– pylorus– pyloric

sphincter

• Stomach motility video

• Stomach Histology

– mucosa


– mucosa: location of gastric glands


– mucosa: location of gastric glands

• gastric gland cells

– mucous cells

– parietal cells

– chief cells

– endocrine cells

• Stomach Histology, continued

– muscularis: three layers

• Stomach Functions– food reservoir– formation of chyme– some chemical digestion– regulation of chyme entry into

S.I.– intrinsic factor production– some absorption

Digestive System, review

• Basic Divisions

– Digestive tract

– Accessory organs: various exocrine glands

• Pancreas

– Location

• Umbilical region

• Pancreas

– Location

• Umbilical region

• Retroperitoneal

• Pancreas Gross Structure

– Head

– Body

– Tail

• Pancreas Gross Structure

– Head

– Body

– Tail

– Ducts

• pancreatic

• accessory

– pancreas histology

• mostly glandular epithelium

– exocrine pancreas

– endocrine pancreas

– exocrine pancreas

• functions

– sodium bicarbonate

– digestive enzymes


• structure: thousands of islets of Langerhans


• function: hormone secretion

– glucagon

– insulin

– somatostatin

• Liver

–Location: epigastric and right hypochondriac regions

• Liver

–Gross structure: 2 major lobes separated by the falciform ligament

• Liver Blood Supply

– Hepatic portal vein

– Hepatic arteries

• Liver Histology

– Functional unit:

• Liver Histology

– Functional unit: liver lobule

• Liver Histology


– Liver cells

• Liver Histology


– Liver cells

• hepatocytes

• Kupffer cells

– Each liver lobule supplied by branches of:

• hepatic arteries

• hepatic portal veins

– Liver Functions

• Maintains blood glucose levels

• Cholesterol synthesis

• HDL and LDL synthesis

• Plasma protein synthesis

– Liver Functions, continued

• Hormone and drug removal

• Phagocytosis

• Vitamin storage

• Iron storage

• Bilirubin excretion

– Liver Functions, continued

• Hormone and drug removal

• Phagocytosis

• Vitamin storage

• Iron storage

• Bilirubin excretion

• Bile salt secretion

• Gall Bladder

– Location: right lumbar region

• Liver Blood Supply

– Hepatic portal vein

– Hepatic arteries

• Gross Structural Features of Gall Bladder

– Muscular sac

– Mucosa folded into rugae

– Bile enters and leaves through cystic duct

• Gall Bladder Function

– Stores and concentrates bile

– Contracts during meals to force bile into SI

• Biliary Pathway

• Biliary Pathway: “plumbing” which drains bile

• Small Intestine

– 1 inch diameter

– 10-20 ft. in length

• duodenum (10 in)

• jejunum (3-6 ft.)

• ileum (6-12 ft)

• Features of SI mucosa

– Plica circularis


–Plica circularis

–Villi


–Plica circularis

–Villi

–Microvilli

• Features of SI mucosa, cont’d

–Epithelial cell types:

•absorptive cells

•Goblet cells

•Endocrine cells

•Paneth cells


–MALT in lamina propria


–MALT in lamina propria

–Intestinal glands (“crypts”)

• Features of SI submucosa

–Submucosal glands in duodenum

• Motility of SI

–Segmentation movements

–Peristalsis

• Functions of small intestine

– Completion of chemical digestion

• “brush-border” enzymes required

– Absorption

– Endocrine control of some digestive processes

Summary movie

• Large Intestine

• Large Intestine (large bowel)

• Large Intestine (large bowel)

–2.5 inches

in diameter

• 5-6 feet long–Cecum –Colon

•Ascending•Transverse•Descending•Sigmoid

–Rectum–Anal canal

• Features of LI mucosa– no villi– numerous

intestinal glands– goblet and

absorptive cells in epithelium

– MALT in lamina propria

• Structural

Features of cecum and colon

– Taeniae coli

– Haustra

– Epiploic appendages

• Other Structural Features

– Vermiform appendix



– Ileocecal valve



– Ileocecal valve

– Stretch receptors in rectum

• initiate defecation reflex



– Ileocecal valve

– Stretch receptors in rectum

• initiate defecation reflex

– Anal sphincters of anal canal

• Motility of Large Intestine

– From cecum to transverse colon:

• peristalsis

– From transverse colon to rectum:

• mass movements

• Functions of Large Intestine

– Water and electrolyte absorption

– Feces formation

– Defecation

• Large Intestinal Bacteria

– Coat surface of mucosa

– Examples: E. coli

– Keep out pathogenic bacteria

Digestive System Basic Divisions – Digestive tract – Accessory organs: various exocrine glands.

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Transcript of Digestive System Basic Divisions – Digestive tract – Accessory organs: various exocrine glands.