the digestive system · digestive system organization •descending colon •sigmoid colon...

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The Digestive System 1 Dr. A. K.Goudarzi D.V.M. Ph.D Department of basic sciences School of veterinary mendicine I.A. University

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Page 1: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

The Digestive System

1

Dr. A. K.Goudarzi D.V.M. Ph.DDepartment of basic sciences

School of veterinary mendicine

I.A. University

Page 2: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Digestion

• Processing of food

• Types

– Mechanical (physical)

• Chew

• Tear

• Grind

• Mash

• Mix

– Chemical

• Catabolic reactions

• Enzymatic hydrolysis

– Carbohydrate

– Protein

– Lipid

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Digestion

• Phases

– Ingestion: taking food into mouth

– Mastication: chewing food & mixing it with saliva

– Deglutition: swallowing food

– Peristalsis: rhythmic wave-like contractions that

move food through GI tract

– Absorption: entering the nutrients to the blood

Page 4: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Secretion

4

• Includes release of exocrine & endocrine

products into GI tract

• Exocrine secretions include: HCl, H20, HC03-,

bile, lipase, pepsin, amylase, trypsin, elastase, &

histamine

• Endocrine includes hormones secreted into

stomach & small intestine to help regulate GI

system

– E.g. gastrin, secretin, CCK, GIP, GLP-1, guanylin,

VIP, & somatostatin

Page 5: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Digestive System Organization

• Gastrointestinal (Gl) tract (Alimentary canal)

– Structures• Mouth

• Oral Cavity

• Pharynx

• Esophagus

• Stomach

• Duedenum

• Jejenum

• Ileum

• Cecum

• Ascending colon

• Transverse colon

Page 6: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Digestive System Organization

• Descending colon

• Sigmoid colon

• Rectum

• Anus

• Accessory structures

– Not in tube path

– Organs

• Teeth

• Tongue

• Salivary glands

• Liver

• Gall bladder

• Pancreas

Page 7: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Layers of GI Tract

7

• Are called tunics

• The 4 tunics are mucosa, submucosa,

muscularis, & serosa

Page 8: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Mucosa• Is the absorptive & secretory layer lining lumen of GI tract

• In places is highly folded with villi to increase absorptive area

• Contains lymph nodules, mucus-secreting goblet cells, & thin layer of muscle

Page 9: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Submucosa

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• Is a thick, highly vascular layer of connective tissue where absorbed molecules enter blood & lymphatic vessels

• Contains glands & nerve plexuses (submucosalplexus) that carry ANS activity to muscularismucosae

Page 10: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Muscularis

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• Is responsible for segmental contractions & peristaltic movement through GI tract

• Has an inner circular & outer longitudinal layer of smooth muscle

– Activity of these layers moves food through tract while pulverizing & mixing it

– Myenteric plexus between these layers is major nerve supply to GI tract

• Includes fibers & ganglia from both Symp & Parasymp systems

Page 11: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Serosa

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• Is outermost layer; serves to bind & protect

• Consists of areolar connective tissue covered with

layer of simple squamous epithelium

Page 12: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

Regulation of GI Tract

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• Parasympathetic effects, arising from vagus &

spinal nerves, stimulate motility & secretions of

GI tract

• Sympathetic activity reduces peristalsis &

secretory activity

• GI tract contains an intrinsic system that controls

its movements--the enteric nervous system

• GI motility is influenced by paracrine & hormonal

signals

Page 13: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Anatomy of the Mouth and

Throat

Page 14: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Human Deciduous and

Permanent Teeth

Page 15: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Dorsal Surface of the Tongue

Page 16: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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The Major Salivary Glands

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Deglutition (swallowing)

• Sequence

– Voluntary stage

• Push food to back of mouth

– Pharyngeal stage

• Raise

– Soft palate

– Larynx + hyoid

– Tongue to soft palate

– Esophageal stage

• Contract pharyngeal muscles

• Open esophagus

• Start peristalsis

Page 18: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Deglutition (swallowing)

• Control

– Nerves

• Glossopharyngeal

• Vagus

• Accessory

– Brain stem

• Deglutition center

– Medulla oblongata

– Pons

– Disorders

• Dysphagia

• Aphagia

Page 19: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Esophagus

• Usually collapsed (closed)

• 3 constrictions

– Aortic arch

– Left primary bronchus

– Diaphragm

• Surrounded by

– SNS plexus

– Blood vessels

• Functions

– Secrete mucous

– Transport food

Page 20: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Peristalsis and Segmentation

Page 21: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Esophagus

• Sphincters

– Upper

– Lower

• Abnormalities

– Achalasia

– Atresia

– Hernia

– Barret’s esophagus

– Esophageal varices

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Page 23: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Stomach

• Gastric glands contain cells that secrete different products that form gastric juice

– Goblet cells secrete mucus

– Parietal cells secrete HCl & intrinsic factor (necessary for B12

absorption in intestine)

– Chief cells secrete pepsinogen (precursor for pepsin)

Page 24: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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• Enterochromaffin-like cells secrete histamine & serotonin

• G cells secrete gastrin

• D cells secrete somatostatin

Stomach

Page 25: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Anatomy of the Stomach

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Stomach

• 3 muscle layers

– Oblique

– Circular

– Longitudinal

• Regions

– Cardiac sphincter

– Fundus

– Antrum (pylorus)

– Pyloric sphincter

• Vascular

• Inner surface thrown into folds – Rugae

• Contains enzymes that work best at pH 1-2

Page 27: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Stomach

• Functions

– Mix food

– Reservoir

– Start digestion of

• Protein

• Nucleic acids

• Fats

– Activates some enzymes

– Destroy some bacteria

– Makes intrinsic factor – B 12 absorption

– Destroys some bacteria

– Absorbs

• Alcohol

• Water

• Lipophilic acid

• B 12

Page 28: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

HCl in Stomach

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• Is produced by parietal cells which AT H+ into lumen via an H+/ K+

pump (pH ≈1)

• Cl- is secreted by facilitated diffusion

• H+ comes from dissociation of H2CO3

• Cl- comes from blood side of cell in exchange for HC03

-

Page 29: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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• Is secreted in response to the

hormone gastrin; & ACh from

vagus

– These are indirect effects since both

stimulate release of histamine which

causes parietal cells to secrete HCl

HCl in Stomach

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• Makes gastric juice very acidic which denatures proteins to make them more digestible

• Converts pepsinogeninto pepsin

– Pepsin is more active at low pHs

HCl in Stomach

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Digestion & Absorption in

Stomach

• Proteins partially digested by pepsin

• Carbohydrate digestion by salivary

amylase is soon inactivated by acidity

• Alcohol & aspirin are only commonly

ingested substances absorbed

Page 32: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Small Intestine

• Extends from pyloric sphincter

ileocecal valve

• Regions

– Duodenum

– Jejenum

– Ileum

• Movements

– Segmentation

– Peristalsis

Page 33: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Small Intestine• Histology

– Intestinal glands – Intestinal enzymes

– Duodenal glands – Alkaline mucous

– Paneth cells – Lysozyme

– Microvilli

– Lacteals

– Plica circularis

– Smooth muscle

– Lymphatic tissue – GALT

– Vascular

Page 34: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Small Intestine

• Absorbs

– 80% ingested water

– Electrolytes

– Vitamins

– Minerals

– Carbohydrates

• Active/facilitated transport

• Monosaccharides

– Proteins

• Di-/tripeptides

• Amino acids

– Lipids

• Monoglycerides

• Fatty acids

• Micelles

• Chylomicrons

Page 35: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Structure of the Villi in the

Small Intestine

Page 36: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Small Intestine

• Secretes digestive enzymes

– Peptidases

• Amino-

• Di-

• Tri-

– Sucrases

– Maltase

– Lactase

– Saccharidases

• Di-

• Tri-

– Lipase

– Nucleases

Page 37: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Small Intestine

• Control

• Requires pancreatic

enzymes & bile to

complete digestion

Page 38: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Large Intestine

• Extends from ileocecal valve to anus

• Regions

– Cecum – Appendix

– Colon

• Ascending

• Transverse

• Descending

– Rectum

– Anal canal

Page 39: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Anatomy of the Large Intestine

Page 40: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Large Intestine

• Histology

– No villi

– No permanent circular folds

– Smooth muscle

• Taeniae coli

• Haustra

– Epiploic appendages

– Otherwise like rest of Gl tract

Page 41: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Large Intestine

• Functions

– Mechanical digestion

• Haustral churning

• Peristalsis

• Reflexes

– Gastroileal

– Gastrocolic

– Chemical digestion –

Bacterial digestion

• Ferment carbohydrates

• Protein/amino acid

breakdown

– Absorbs

•More water

•Vitamins

– B

– K

– Concentrate/eliminate wastes

Page 42: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Feces Formation and Defecation

• Chyme dehydrated to form feces

• Feces composition

– Water

– Inorganic salts

– Epithelial cells

– Bacteria

– Byproducts of digestion

• Defecation

– Peristalsis pushes feces into rectum

– Rectal walls stretch

• Control

– Parasympathetic

– Voluntary

Page 43: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Liver

• Location

– R. Hypochondrium

– Epigastric region

• 4 Lobes

– Left

– Quadrate

– Caudate

– Right

• Each lobe has lobules – Contains hepatocytes –Surround sinusoids – Feed into central vein

Page 44: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Liver

• Functions

– Makes bile

• Detergent – emulsifies fats

• Release promoted by:

– Vagus n.

– CCK

– Secretin

• Contains

– Water

– Bile salts

– Bile pigments

– Electrolytes

– Cholesterol

– Lecithin

Page 45: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Liver

– Detoxifies/removes

• Drugs

• Alcohol

– Stores

• Glycogen

• Vitamins (A, D, E, K)

• Fe and other minerals

• Cholesterol

– Activates vitamin D

– Fetal RBC production

– Phagocytosis

– Metabolizes absorbed food molecules

• Carbohydrates

• Proteins

• Lipids

Page 46: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Liver

• Dual blood supply

– Hepatic portal vein

• Direct input from small

intestine

– Hepatic artery/vein

• Direct links to heart

Page 47: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Liver

Page 48: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Page 49: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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The Duodenum and Related

Organs

Page 50: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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The Organs and Positions in the

Abdominal Cavity

Page 51: The Digestive System · Digestive System Organization •Descending colon •Sigmoid colon •Rectum •Anus • Accessory structures –Not in tube path –Organs •Teeth •Tongue

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Structures of the Alimentary

Canal