Digestive System
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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

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Digestive system function to obtain nutrients

Digestive System

Function:

to obtain nutrients


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


Digestive system function to obtain nutrients

The Digestive System


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


Digestive system function to obtain nutrients

Tunic Mucosa

  • Lines digestive tract

  • Moistened by glandular secretions

  • Simple or stratified depending on area of tract

  • Pleated for expansion (Surface Area)


Digestive system function to obtain nutrients

1. Tunic Mucosa

  • A Mucous membrane

    • 1) Epithelium

    • 2) Lamina propria

    • 3) Muscularis mucosae

2. Tunic Submucosa

  • Areolar Connective Tissue

  • Innervation

  • May have glands


Digestive system function to obtain nutrients

Muscularis Mucosa

  • Smooth muscle layer capable of plasticity

    • Ability to tolerate stretching

  • Visceral smooth muscle


Digestive system function to obtain nutrients

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


Digestive system function to obtain nutrients

Histology of the G.I. Tract


Digestive system function to obtain nutrients

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


Digestive system function to obtain nutrients

  • Retroperitoneal Structures – these are attached to posterior abdominal wall

    • Ascending colon

    • Descending colon

    • Duodenum

    • Pancreas


Salivary glands

Salivary glands

  • Parotid

  • Sublingual

  • Submandibular

    • Slightly different secretions

    • Release enzymes - amylase

    • Lubrication oral cavity


Digestive system function to obtain nutrients

Fig

25.6


Digestive system function to obtain nutrients

Fig

25.7

Only example of gomphosis joint

Incisors -clipping/cutting

Canines-tearing/slashing

Premolars- mashing/grinding

Molarsmashing/grinding


Teeth

Teeth

Regions:

Crown

Neck

Root

Layers:

Enamel

Dentin

Pulp Cavity with Pulp

Cementum

Apical foramen

Root canal

Periodontal membrane


Digestive system function to obtain nutrients

Voluntary control

Pharynx and Esophagus

Deglutition

Swallowing

Epiglottis closes over larynx


Digestive system function to obtain nutrients

Tunica muscularis has three layers of muscle

Fig

25.11

Tunica mucosa has folds, rugae when empty


Digestive system function to obtain nutrients

Histology of Gastric glands

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

  • Secretin and cholecystokinin

    • Inhibit gastric secretion


Digestive system function to obtain nutrients

Small Intestine

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


Digestive system function to obtain nutrients

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


Digestive system function to obtain nutrients

  • Duodenum:

  • Duodenal (Brunner’s) glands produce:

    • secretin

    • CCK

    • Alkaline mucus


Digestive system function to obtain nutrients

Ilieum: lymphatic aggregations (Peyer’s patches)


Secretin

Secretin


Digestive system function to obtain nutrients

CCK


Digestive system function to obtain nutrients

  • Large 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


Digestive system function to obtain nutrients

Histology of Large Intestine

Large Intestine:

Lack of villi

Abundance of goblet cells

Mucous-secreting intestinal glands

Muscularis reduced to Taenia coli

Fatty appendices


Digestive system function to obtain nutrients

Rectum and Anal canal


Digestive system function to obtain nutrients

Other digestive organs

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


Liver

Liver


Bile ducts

Bile Ducts


Digestive system function to obtain nutrients

Diagrammatic view of lobular organization.


Pancreas

Pancreas


Etoh on liver

EtOH on Liver


Pancreas1

Pancreas


Pancreas2

Pancreas

Exocrine: acini

Endocrine:

Pancreatic islets

Isles of Langerhans


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