Overview of the digestive system
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Overview of the Digestive System. Digestive Tract: Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon) Accessory Organs: Teeth, tongue, salivary glands, pancreas, liver, and gallbladder. Components of the Digestive System. GI Tract: Oral Cavity Pharynx

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Overview of the Digestive System

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Overview of the Digestive System

Digestive Tract:

Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon)

Accessory Organs:

Teeth, tongue, salivary glands, pancreas, liver, and gallbladder


Components of the Digestive System

  • GI Tract:

  • Oral Cavity

  • Pharynx

  • Esophagus

  • Stomach

  • Small Intestine

  • Large Intestine


Teeth


Oral Cavity


The Pharynx

  • Nasopharynx

  • Oropharynx

  • Laryngopharynx


Salivary Glands


The Esophagus


Peristalsis in Esophagus

LE 21-8

Muscles contract

Muscles

contract,

constricting

passageway

and pushing

bolus down

Muscles relax

Bolus of

food

Muscles relax,

allowing

passageway

to open

Muscles contract

Muscles

relax

Stomach


Stomach

  • Site where food is churned into chyme

  • Protein digestion begins


Stomach


Stomach


LE 21-11a

Duodenum and Related Organs

Liver

Bile

Gall-

bladder

Stomach

Bile

Pancreas

Acid chyme

Intestinal enzymes

Pancreatic

juice

Duodenum of

small intestine


Duodenum and Related Organs


Small Intestine – Gross Anatomy

  • Longest portion of the alimentary canal

  • Site of most enzymatic digestion and absorption

  • Three subdivisions

    • Duodenum, jejunum, and ileum


Gross Anatomy of Large Intestine

  • Cecum

  • Appendix

  • Ascending

  • Transverse

  • Descending

  • Sigmoid colon

  • Rectum

  • Anus


LE 21-12

Large

intestine

(colon)

Small

intestine

Sphincter

End

of small

intestine

Rectum

Anus

Nutrient

flow

Appendix

Cecum


Gross Anatomy of Large Intestine

  • Rectum – descends along the inferior half of the sacrum

  • Anal Canal – the last subdivision of the large intestine


Pancreas


Gallbladder

  • Stores and concentrates bile

  • Expels bile into duodenum

    • Bile emulsifies fats


Gallbladder


Visceral Surface of the Liver


Histology of the Digestive Tract

Mucosa

Submucosa

Muscularis Externa

Serosa


Mucosa (Innermost Layer)

  • Epithelium

  • Connective Tissue (Blood vessels, lymphatic vessels, lymphatic nodules)

  • Smooth Muscle


Submucosa

Connective tissue

  • Blood vessels

  • Lymphatic vessels

  • Nerve plexus

  • May have glands and lymphatic tissue


Muscularis Externa

Smooth or Skeletal Muscle

If smooth muscle, usually 2 layers (circular and longitudinal)


Adventitia or Serosa

Adventitia (organs superior to diaphragm)

Serosa = visceral peritoneum


The Esophagus

  • Stratified squamous epithelium

  • Mucous glands

  • Muscularis externa – skeletal muscle first third of length


Stomach – Microscopic Anatomy


Stomach – Microscopic Anatomy


Small Intestine: Peyer’s Patches


The Stomach – Microscopic Anatomy


The Small Intestine – Structural Features


Small Intestine – Microscopic Anatomy


LE 21-11b

Lumen of intestine

Nutrient

absorption

Vein

with blood

en route to

the liver

Nutrient absorption

into epithelial cells

Microvilli

Epithelial

cells

Amino

acids

and

sugars

Fatty

acids

and

glycerol

Lumen

Muscle

layers

Fats

Blood

capillaries

Large

circular folds

Blood

Villi

Lymph

vessel

Lymph

Nutrient

absorption

Epithelial cells

Villi

Intestinal wall


Small Intestine: Duodenum

Br = Brunner glands

V = Villus

G = Goblet cells

Cr = Intestinal glands

MM = Muscularis

Mucosae

LP = Lamina Propria


Microscopic Anatomy of Large Intestine

  • Villi are absent

  • Contains numerous goblet cells

  • Intestinal crypts – simple tubular glands

  • Lined with simple columnar epithelial tissue

  • Epithelium changes at anal canal

    • Becomes stratified squamous epithelium


Microscopic Anatomy of Large Intestine


Liver

  • Largest gland in the body

  • Performs over 500 functions

  • Digestive function – bile production

  • Performs many metabolic functions


Microscopic Anatomy of Liver


Microscopic Anatomy of Liver


The Peritoneal Cavity and Peritoneum

  • Mesentery – a double layer of peritoneum

    • Holds organs in place

    • Sites of fat storage

    • Provides a route for circulatory vessels and nerves


Mesenteries

  • Superficial view of the abdominal organs


Mesenteries

  • Greater omentum and transverse colon reflected


Mesenteries

  • Sagittal section through the abdominopelvic cavity


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