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Digestive System Function: to obtain nutrients. Digestive System Function: obtaining nutrients. Activities of Digestion system: Ingestion – taking food or liquid into the mouth (eating or drinking). Movements Peristaltic and Segmentation Digestion Mechanical mastication

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Digestive System

Function:

to obtain nutrients


Digestive System

Function: obtaining nutrients

  • Activities of Digestion system:

    • Ingestion – taking food or liquid into the mouth (eating or drinking).

    • Movements

      • Peristaltic and Segmentation

    • Digestion

      • Mechanical

        • mastication

        • churning

      • Chemical

        • Enzymes and acids

    • Absorption – movement of substances into the body (across epithelium).

    • Elimination – involves compaction to eliminate waste from body



Layers of gastrointestinal tract
Layers of Gastrointestinal Tract

  • Four layers:

    • Know layers and their composition

  • Tunic mucosa

    • Epithelial

    • Propria

    • Muscularis mucosae

  • Tunic submucosa

  • Tunica muscularis externa

  • Tunica serosa-visceral peritoneum


Tunic Mucosa

  • Lines digestive tract

  • Moistened by glandular secretions

  • Simple or stratified depending on area of tract

  • Pleated for expansion (Surface Area)


1. Tunic Mucosa

  • A Mucous membrane

    • 1) Epithelium

    • 2) Lamina propria

    • 3) Muscularis mucosae

2. Tunic Submucosa

  • Areolar Connective Tissue

  • Innervation

  • May have glands


Muscularis Mucosa

  • Smooth muscle layer capable of plasticity

    • Ability to tolerate stretching

  • Visceral smooth muscle


3. Tunica Muscularis Externa

  • Smooth muscle layers

  • 1) Inner Circular Layer

  • 2) Outer Longitudinal Layer

4. Tunica Serosa (or Adventitia*)

Serous membrane – visceral peritoneum

  • * Name depends on location:

  • Inside peritoneal cavity = serosa

  • Outside peritoneal cavity = adventitia



Serous Membranes

  • The Peritoneum: Two layers

    • Visceral peritoneum (a.k.a serosa)

    • Parietal peritoneum

      • Lines inner surfaces of body wall

  • Mesenteries: Fused double sheets of peritoneal membrane – to suspend portions of digestive tract:

    • Greater omentum

    • Lesser omentum

    • Mesentery proper

    • Transversemesocolon

    • Sigmoid mesocolon



Salivary glands
Salivary glands posterior abdominal wall

  • Parotid

  • Sublingual

  • Submandibular

    • Slightly different secretions

    • Release enzymes - amylase

    • Lubrication oral cavity


Fig posterior abdominal wall

25.6


Fig posterior abdominal wall

25.7

Only example of gomphosis joint

Incisors -clipping/cutting

Canines-tearing/slashing

Premolars- mashing/grinding

Molarsmashing/grinding


Teeth
Teeth posterior abdominal wall

Regions:

Crown

Neck

Root

Layers:

Enamel

Dentin

Pulp Cavity with Pulp

Cementum

Apical foramen

Root canal

Periodontal membrane


Voluntary control posterior abdominal wall

Pharynx and Esophagus

Deglutition

Swallowing

Epiglottis closes over larynx


Tunica muscularis has three layers of muscle posterior abdominal wall

Fig

25.11

Tunica mucosa has folds, rugae when empty


Histology of Gastric glands posterior abdominal wall

Chief - Pepsinogen; Parietal - HCl; Neck/Mucous Cells

  • Secretin and cholecystokinin

    • Inhibit gastric secretion


Small Intestine posterior abdominal wall

Duodenum

Jejunum

Ileum

Increase Surface Area for Absorption

Plicae Circulares

Intestinal villi

Microvilli

  • Lacteal (terminal lymphatic)

  • for lipid absorption

  • Intestinal glands

    • Goblet cells

    • Stem cells


Diagrammatic view highlighting the distinguishing features of each region of the small intestine.


  • Duodenum: of each region of the small intestine.

  • Duodenal (Brunner’s) glands produce:

    • secretin

    • CCK

    • Alkaline mucus


Ilieum: lymphatic aggregations (Peyer’s patches) of each region of the small intestine.


Secretin
Secretin of each region of the small intestine.


CCK of each region of the small intestine.


  • Large intestine of each region of the small intestine.

  • Functions of large intestine

    • Reabsorb water and compact feces

    • Absorb vitamins

    • Store fecal matter

  • Cecum

    • Ileocecal valve

    • Collects material from small intestine

    • Vermiform appendix

  • Colon - ascending, transverse, descending and sigmoid

  • Rectum


Histology of Large Intestine of each region of the small intestine.

Large Intestine:

Lack of villi

Abundance of goblet cells

Mucous-secreting intestinal glands

Muscularis reduced to Taenia coli

Fatty appendices


Rectum and Anal canal of each region of the small intestine.


Other digestive organs of each region of the small intestine.

Horizontal section through the upper abdomen showing the position of the liver relative to other visceral organs.


Liver
Liver of each region of the small intestine.


Bile ducts

Bile Ducts of each region of the small intestine.


Diagrammatic view of lobular organization. of each region of the small intestine.


Pancreas
Pancreas of each region of the small intestine.


Etoh on liver
EtOH on Liver of each region of the small intestine.


Pancreas1
Pancreas of each region of the small intestine.


Pancreas2
Pancreas of each region of the small intestine.

Exocrine: acini

Endocrine:

Pancreatic islets

Isles of Langerhans


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