LESSON NOTES. DIGESTIVE SYSTEM NATUNGA RONALD.ppt

NATUNGA ANATOMY

1. DIGESTIVE SYSTEM ANATOMY AND
PHYSIOLOGY
BUYO REMALIAH ISRON

2. Functional Anatomy of the
Digestive System

3. Plan
•Viscera
•Digestive System

4. CLASSIFICATION OF THE INTERNAL ORGANS
According to functional point of view the viscera are divided into
systems of organs and apparatuses.
•Digestive system (energy, nutrients for growing up ) /the mouth,
esophagus, gastrointestinal tract, liver and pancreas and salivary
glands/;
•Respiratory system (exchange of gases O2 to support
burning)/(the nose, airways, larynx and lungs);
•Urogenital system (excretion also skin)(the urinary and genital or
reproductive organs) – (multiplication);
•Controlling system Endocrine and Nervous systems (the ductless
glands and cells which produce hormones);
•Circulatory system (the heart and blood and lymph vessels);
•Defense system (the blood, lymphatics and bone marrow);

5. GENERAL PLAN OF DIGESTIVE TRACT
•With specific modifications at different
organs the structure of GIT is as below.
•The mucous coat ( tunica mucosa )
•The submucous layer ( tela submucosa )
•The muscular coat (tunica muscularis )
•The serous coat (tunica serosa ), or the
adventitious coat ( tunica adventitia )

7. The Structure of the Digestive Tract

9. Right
Hypoch
ondriac
Epigastric
Left hypo
chondriac
Central or
Umblical
Right
lumbar
Left
lumbar
Right
iliac
Left
iliac
Hypogastric
Or supra pubic

10. Digestive System
•The digestive system, or alimentary
system (systema digestorium) is a complex
of organs which provides:
Mechanical and chemical treatment of
food,
Absorption of the treated nutrients, and
Excretion of undigested remnants of
the food.

11. The Components of the Digestive System

13. Layers of digestive wall

15. Functions of the digestive system
•Ingestion
•Mechanical processing
•Chemical processing
•Digestion
•Secretion
•Absorption
•Excretion

16. Movement of digestive materials
•Visceral smooth muscle shows rhythmic cycles
of activity
–Pacemaker cells in the oesophagus start it
•Peristalsis
–Waves that move a bolus
•Segmentation
–Churn and fragment a bolus

17. Peristalsis
Figure 24.4

18. THE MOUTH AND STRUCTURES
ASSOCIATED

19. •Lips (labia) – protect the anterior
opening
•Cheeks – form the lateral walls
•Hard palate – forms the anterior roof
•Soft palate – forms the posterior roof
•Uvula – fleshy projection of the soft
palate

20. The tongue
•Primary functions include:
–Mechanical processing
–Assistance in chewing and swallowing
–Sensory analysis by touch, temperature,
and taste receptors

21. General function of oral cavity
•Sensory analysis
–Of material before swallowing
•Mechanical processing
–Through actions of teeth, tongue, and palatal
surfaces
•Lubrication
–Mixing with mucus and salivary gland secretions
•Limited digestion
–Of carbohydrates and lipids by salivary amylase

22. The pharynx
•Common passageway for food, liquids, and air
•Depicts typical basic structure of alimentary
canal
•Lined with stratified squamous epithelium
•Pharyngeal muscles assist in swallowing
–Pharyngeal constrictor muscles
–Palatal muscles
Refer to respiratory system for details.

23. Esophagus
•A hollow muscular tube
•About 25 cm (10 in.) long and 2 cm (0.80 in.)
wide
•Enters abdominal cavity at oesophageal hiatus
•Conveys solid food and liquids to the stomach
•Begins posterior to cricoid cartilage
•Is innervated by fibers from the esophageal
nervesplexus

25. Histology of the esophagus
•Distinctive features of the esophageal wall
include
–Nonkeratinized, stratified squamous epithelium
–Folded mucosa and submucosa
•Mucous secretions by esophageal glands
–A muscular layer with both smooth and skeletal
muscle portions
–Lacks serosa
•Anchored by an adventitia

26. Functions of oesophagus
•Peristaltic movement of food
•Lubrication of food

27. The Stomach

28. The Stomach Lining

29. The Stomach Lining

30. Histology of the stomach
•Gastric glands have.
–Parietal cells
Produce Intrinsic factor, responsible for VIT B12
absorption
–Chief cells
•Produce Pepsinogen
•Pyloric glands

31. Digestion and absorption in the
stomach
•Preliminary digestion of proteins
–Pepsin produced from pepsinogen by the action of HCL
•Permits digestion of carbohydrates
•Very little absorption of nutrients
–Some drugs, however, are absorbed
–Mucous secretion containing several hormones
•Enteroendocrine cells
–G cells secrete gastrin
–D cells secrete somatostatin

32. Functions of the stomach
•Bulk storage of undigested food
•Proper mixing of food by chuning effects
•Mechanical breakdown of food
•Disruption of chemical bonds via acids and
enzymes. Chemical digestion of proteins
•Production of intrinsic factor

33. Small intestine
•Important digestive and absorptive functions
–Secretions and buffers provided by pancreas, liver,
gall bladder
•Three subdivisions:
–Duodenum
–Jejunum
–Ileum
•Ileocecal sphincter
–Transition between small and large intestine

34. Regions of the Small Intestine

35. Small Intestine
•The Duodenum
–The segment of small intestine closest to stomach
–25 cm (10 in.) long
–“Mixing bowl” that receives chyme from stomach
and digestive secretions from pancreas and liver
–Functions of the duodenum
•To receive chyme from stomach
•To neutralize acids before they can damage the
absorptive surfaces of the small intestine

36. Small Intestine
•The Jejunum
–Is the middle segment of small intestine
–2.5 meters (8.2 ft) long
–Is the location of most
•Chemical digestion
•Nutrient absorption
–Has few plicae circulares
–Small villi

37. Small Intestine
•The Ileum
–The final segment of small intestine
–3.5 meters (11.48 ft) long
–Ends at the ileocecal valve, a sphincter that
controls flow of material from the ileum
into the large intestine

38. Histology of the small intestine
•Plicae
–Transverse folds of the intestinal lining
•Villi
–Fingerlike projections of the mucosa
•Lacteals
–Terminal lymphatic in villus
•Intestinal glands
– Lined by enteroendocrine, goblet and stem cells

39. The Intestinal Wall

40. The Intestinal Wall: the villus

41. Small Intestine
•Duodenal glands (Brunner’s glands)
–produce mucus, buffers, urogastrone
•Ileum
–aggregated lymphoid nodules (Peyer’s patches)

42. Intestinal movements
•Peristalsis
•Segmentation
•Gastroenteric reflexes
–Initiated by stretch receptors in stomach
•Gastroileal reflex
–Triggers relaxation of ileocecal valve

43. Small Intestine
•Intestinal Secretions
–Watery intestinal juice
–1.8 liters per day enter intestinal
lumen
–Moisten chyme
–Assist in buffering acids
–Keep digestive enzymes and
products of digestion in solution

44. •Intestinal Movements
–Chyme arrives in duodenum
–Weak peristaltic contractions move it slowly
toward jejunum
•Myenteric reflexes
•Not under CNS control
•Parasympathetic stimulation accelerates local
peristalsis and segmentation

45. The pancreas
•Pancreatic duct penetrates duodenal wall
•Endocrine functions
–Insulin secreted by beta cells and glucagons secreted
by alpha cells of islets of langerhans
•Exocrine functions
–Majority of pancreatic secretions
–Pancreatic juice secreted into small intestine
•Carbohydrases
•Lipases
•Nucleases
•Proteolytic enzymes

46. The Pancreas

47. Pancreas
•Pancreatic Enzymes
–Pancreatic alpha-amylase
•A carbohydrase
•Breaks down starches
•Similar to salivary amylase
–Pancreatic lipase
•Breaks down complex lipids
•Releases products (e.g., fatty acids) that are
easily absorbed.easily absorbed

48. •Pancreatic Enzymes
–Nucleases
•Break down nucleic acids
–Proteolytic enzymes
•Break certain proteins apart
•Proteases break large protein complexes
•Peptidases break small peptides into amino
acids
•70% of all pancreatic enzyme production
•Secreted as inactive proenzymes
•Activated after reaching small intestine

49. The Liver
•Performs metabolic and hematological
regulation and produces bile
•Histological organization
–Lobules containing single-cell thick plates of
hepatocytes
–Lobules unite to form common hepatic duct
•Duct meets cystic duct to form common bile duct

50. The Anatomy of the Liver

51. The Anatomy of the Liver

52. HEXAGONAL LIVER CELLS

53. Liver Histology

54. Liver Function
The Physiology of the Liver
1.Metabolic regulation
2.Hematological regulation
3.Bile production

55. Liver Function
•Metabolic Regulation
–The liver regulates:
1.Composition of circulating blood
2.Nutrient metabolism (carbohydrate, lipid & amino
acid)
3.Waste product removal
4.Vitamin Storage (A, D, E & K)
5.Nutrient storage (iron)
6.Drug inactivation

56. Liver Function
•Composition of Circulating Blood
–All blood leaving absorptive surfaces of digestive tract
•Enters hepatic portal system
•Flows into the liver
–Liver cells extract nutrients or toxins from blood
•Before they reach systemic circulation through hepatic
veins
–Liver removes and stores excess nutrients
•Corrects nutrient deficiencies by mobilizing stored
reserves or performing synthetic activities. activities

57. Liver Function
•Hematological Regulation
–Largest blood reservoir in the body
•Receives 25% of cardiac output
•Functions of Hematological Regulation
1.Phagocytosis and antigen presentation
2.Synthesis of plasma proteins
3.Removal of circulating hormones
4.Removal of antibodies
5.Removal or storage of toxins
6.Synthesis and secretion of bile

58. Liver Function
•The Functions of Bile
–Dietary lipids are not water soluble
–Mechanical processing in stomach creates large
drops containing lipids
–Pancreatic lipase is not lipid soluble
•Interacts only at surface of lipid droplet
–Bile salts break droplets apart (emulsification)
•Increases surface area exposed to enzymatic
attack
•Creates tiny emulsion droplets coated with bile salts

59. The gallbladder
•Hollow, pear-shaped organ
•Stores, modifies and concentrates bile
•Stores and releases bile salt

60. The Gallbladder

61. Gallbladder
•Is a pear-shaped, muscular sac
•Stores and concentrates bile prior to excretion
into small intestine
•Is located in the fossa on the posterior surface
of the liver’s right lobe
•The Cystic Duct
–Extends from gallbladder
–Union with common hepatic duct forms common
bile duct

62. Gallbladder
•Functions of the Gallbladder
–Stores bile
–Releases bile into duodenum, but only under stimulation
of hormone cholecystokinin (CCK)
–CCK
•Hepatopancreatic sphincter remains closed
•Bile exiting liver in common hepatic duct cannot flow
through common bile duct into duodenum
•Bile enters cystic duct and is stored in gallbladder

63. Large intestine ( colon)
•Ceacum
•Appendix
•Ascending colon
•Transverse colon
•Descending colon
•Rectum
•Anus

65. Large Intestine
•Is horseshoe shaped
•Extends from end of ileum to anus
•Lies inferior to stomach and liver
•Frames the small intestine
•Also called large bowel
•Is about 1.5 meters (4.9 ft) long and 7.5 cm (3 in.)
wide

66. Large Intestine Functions
–Reabsorption of water
–Compaction of intestinal contents into
feces
–Absorption of important vitamins
produced by bacteria
–Storage of fecal material prior to
defecation

67. Parts of Large Intestine
•The Cecum
–Is an expanded pouch
–Receives material arriving from the ileum
–Stores materials and begins compaction
•Appendix
–Also called vermiform appendix
–Is a slender, hollow appendage about 9 cm (3.6
in.) long
–Is dominated by lymphoid nodules (a lymphoid
organ organ)

68. Parts of Large Intestine
•The Colon
–Has a larger diameter and thinner wall than small
intestine
–The wall of the colon
•Forms a series of pouches (haustra)
–Haustra permit expansion and elongation of colon

69. Parts of Colon
•Ascending Colon
–Begins at superior border of cecum
–Ascends along right lateral and posterior wall of peritoneal
cavity to inferior surface of the liver and bends at right
colic flexure (hepatic flexure)
•Transverse Colon
–Crosses abdomen from right to left; turns at left colic
flexure (splenic flexure)
–Is supported by transverse mesocolon
–Is separated from anterior abdominal wall by greater
omentum

70. Parts of Colon
•The Descending Colon
–Proceeds inferiorly along left side to the iliac fossa (inner
surface of left ilium)
–Is retroperitoneal, firmly attached to abdominal wall
•The Sigmoid Colon
–Is an S-shaped segment, about 15 cm (6 in.) long
–Starts at sigmoid flexure
–Lies posterior to urinary bladder
–Is suspended from sigmoid mesocolon
–Empties into rectum

71. Parts of Large Intestine
•The Rectum
–Forms last 15 cm (6 in.) of digestive tract
–Is an expandable organ for temporary storage of
feces
–Movement of fecal material into rectum triggers
urge to defecate
•The anal canal is the last portion of the rectum
–Contains small longitudinal folds called anal
columns
•Anus
–Also called anal orifice
–Is exit of the anal canal
–Has keratinized epidermis like skin

73. Histology of the large intestine
•Absence of villi
•Presence of goblet cells
•Deep intestinal glands

74. Physiology of the Large Intestine
•Absorption in the Large Intestine
–Reabsorption of water
–Reabsorption of bile salts
•In the cecum
•Transported in blood to liver
–Absorption of vitamins produced by bacteria
–Absorption of organic wastes

75. Physiology of the Large Intestine
Three Vitamins Produced in the Large Intestine
1.Vitamin K (fat soluble):
•Required by liver for synthesizing four clotting factors, including
prothrombin
2.Biotin (water soluble):
•Important in glucose metabolism
3.Pantothenic acid: B
5 (water soluble):
•Required in manufacture of steroid hormones and some
neurotransmitters

76. Physiology of the Large Intestine
•Organic Wastes
–Bacteria convert bilirubin to urobilinogens and
stercobilinogens
–Bacteria break down peptides in feces and generate
•Ammonia, Indole & skatole, hydrogen sulfide
–Bacteria feed on indigestible carbohydrates (complex
polysaccharides)
•Produce flatus, or intestinal gas, in large intestine

77. Movements of the Large Intestine
•Gastroileal & gastroenteric reflexes
–Move materials into cecum while you eat
–Movement from cecum to transverse colon is
very slow, allowing hours for water absorption
–Peristaltic waves move material along length
of colon
–Segmentation movements (haustral churning)
mix contents of adjacent haustra

78. •Movements from transverse colon through rest of
large intestine results from powerful peristaltic
contractions (mass movements)
•Stimulus is distension of stomach and duodenum;
relayed over intestinal nerve plexuses
•Distension of the rectal wall triggers defecation
reflex
–Two positive feedback loops
–Both loops triggered by stretch receptors in
rectum

79. Digestion
•Digestive system handles each nutrient
differently
–Large organic molecules
•Must be digested before absorption can occur
–Water, electrolytes, and vitamins
•Can be absorbed without processing
•May require special transport

80. Digestion
•Digestive Enzymes
–Break molecular bonds in large organic molecules
•Carbohydrates, proteins, lipids, and nucleic acids
•In a process called hydrolysis
–Are divided into classes by targets
•Carbohydrases break bonds between simple
sugars
•Proteases break bonds between amino acids
•Lipases separate fatty acids from glycerides

81. Digestion
•Water Absorption
–Cells cannot actively absorb or secrete
water
–All movement of water across lining of
digestive tract
•Involves passive water flow down
osmotic gradients