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Overview of the Digestive System

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Presentation on theme: "Overview of the Digestive System"— Presentation transcript:

1 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

2 Functions of the Digestive System
Ingestion Mechanical processing Chemical digestion Secretion Absorption Excretion

3 Histology of the Digestive Tract
Mucosa Submucosa Muscularis Externa Serosa

4 Mucosa (Innermost Layer)
Epithelium Connective Tissue (Blood vessels, lymphatic vessels, lymphatic nodules) Smooth Muscle

5 Submucosa Connective tissue Blood vessels Lymphatic vessels Nerve plexus May have glands and lymphatic tissue

6 Muscularis Externa Smooth or Skeletal Muscle
If smooth muscle, usually 2 layers (circular and longitudinal)

7 Adventitia or Serosa Adventitia (organs superior to diaphragm)
Serosa = visceral peritoneum

8 Small Intestine: Peyer’s Patches

9 Components of the Digestive System
GI Tract: Oral Cavity Pharynx Esophagus Stomach Small Intestine Large Intestine

10 Oral Cavity

11 Oral Cavity

12 The Pharynx Nasopharynx Oropharynx Laryngopharynx

13 The Esophagus

14 The Esophagus Stratified squamous epithelium Mucous glands
Muscularis externa – skeletal muscle first third of length

15 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

16 Stomach Site where food is churned into chyme Protein digestion begins

17 Stomach

18 Stomach

19 Stomach – Microscopic Anatomy

20 Stomach – Microscopic Anatomy

21 The Stomach – Microscopic Anatomy

22 Ulcers in stomach Helicobacter pylori

23 Small Intestine – Gross Anatomy
Longest portion of the alimentary canal Site of most enzymatic digestion and absorption Three subdivisions Duodenum, jejunum, and ileum

24 Duodenum and Related Organs
LE 21-11a Duodenum and Related Organs Liver Bile Gall- bladder Stomach Bile Pancreas Acid chyme Intestinal enzymes Pancreatic juice Duodenum of small intestine

25 Duodenum and Related Organs

26 Enzymes in Small Intestine

27 Small Intestine – Microscopic Anatomy

28 Amino acids and sugars Fatty acids and glycerol
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 Muscle layers Lumen Fats Blood capillaries Large circular folds Villi Blood Lymph vessel Nutrient absorption Lymph Epithelial cells Villi Intestinal wall

29 Small Intestine: Duodenum
Br = Brunner glands V = Villus G = Goblet cells Cr = Intestinal glands MM = Muscularis Mucosae LP = Lamina Propria

30 The Small Intestine – Structural Features

31 Gross Anatomy of Large Intestine
Cecum Appendix Ascending Transverse Descending Sigmoid colon Rectum Anus

32 Large intestine (colon) Sphincter Small intestine End of small
LE 21-12 Large intestine (colon) Sphincter Small intestine End of small intestine Rectum Anus Nutrient flow Appendix Cecum

33 Gross Anatomy of Large Intestine
Rectum – descends along the inferior half of the sacrum Anal Canal – the last subdivision of the large intestine

34 Gross Anatomy of Large Intestine

35 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

36 Microscopic Anatomy of Large Intestine

37 Teeth

38 Salivary Glands

39 Pancreas

40 Exocrine Pancreas: Histology

41 Liver Largest gland in the body Performs over 500 functions
Digestive function – bile production Performs many metabolic functions

42 Visceral Surface of the Liver

43 Microscopic Anatomy of Liver

44 Microscopic Anatomy of Liver

45 Gallbladder Stores and concentrates bile Expels bile into duodenum
Bile emulsifies fats

46 Gallbladder

47 Enzymes in Small Intestine

48 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

49 Mesenteries Superficial view of the abdominal organs

50 Mesenteries Greater omentum and transverse colon reflected

51 Mesenteries Sagittal section through the abdominopelvic cavity

52 Segmentation Rhythmic local contractions of the intestine Mixes food with digestive juices

53 Disorders of the Digestive System
Intestinal obstruction Mechanical obstructions Adhesions, tumors, or foreign objects Nonmechanical obstruction Halt in peristalsis Trauma Intestines touched during surgery

54 Disorders of the Digestive System
Inflammatory bowel disease Inflammation of intestinal wall Crohn’s disease Ulcerative colitis Viral hepatitis – jaundice and flu-like symptoms Major types – A, B, C, and G Cystic Fibrosis and the Pancreas

55 The Digestive System in Later Life
Middle age – gallstones and ulcers Old age – activity of digestive organs decline Fewer digestive juices and enzymes produced Absorption is less efficient Dehydration of fecal mass leads to constipation Diverticulosis and cancer of digestive organs

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