Post on 28-Dec-2015
transcript
1
The Digestive System
2
DIGESTIVE SYSTEM
• Collective name used to describe– The alimentary canal– Some accessory organs– A variety of digestive processes
3
• Ingestion
• Mechanical processing/Propulsion
• Digestion
• Secretion
• Absorption
• Excretion
Functions of the digestive system
4
The Components of the Digestive System
5
• Gastrointestinal (Gl) tract (Alimentary canal)– Tube within a tube
– Direct link/path between organs
– Structures• Mouth
• Oral Cavity
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Rectum and anal canal
Digestive System Organization
6
Digestive System Organization
• Accessory structures– Not in tube path– Organs
• Teeth• Tongue• Salivary glands• Liver• Gall bladder• Pancreas
7
The Structure of the Digestive Tract
12-8
The Wall of the Digestive Tract
The digestive tract wall has four layers:
Mucosa (mucous membrane – secretes digestive enzymes and mucus),
Submucosa (loose connective tissue – houses blood and lymph vessels),
Muscularis (two layers of smooth muscle - for peristalsis), and
Serosa (serous membrane – secretes serous fluid to prevent sticking).
9
10
MOUTH
12-11
Adult mouth
12
Mouth
• The mouth opens into the oral or buccal cavity
• Its functions include:– Analysis of material before swallowing– Mechanical processing by the teeth,
tongue, and palatal surfaces– Lubrication– Limited digestion
Lips and cheeks enclose the mouth.
Taste buds on the tongue provide the sense of taste; skeletal muscle in the tongue allows it to move.
The roof of the mouth is formed by the hard and soft palates that separate it from the nasal cavities.
The soft palate ends in a finger-shaped projection called the uvula.
13
14
TONGUE
15
16
17
Functions Of Tongue
• Mastication (Chewing)
• Deglutition ( Swallowing)
• Speech
• Taste
18
TEETH
19
Structure of tooth
12-20
Adult mouth
21
SALIVARY GLANDS
22
The Major Salivary Glands
23
Structure of salivary gland
24
PHARYNX
25
Pharynx• Divided into 3 parts for descriptive
purpose
Nasopharynx– Important for respiration
Oropharynx
Laryngopharynx– Passages common for both respiratory and
digestive system
26
Pharynx
• Food passes from the oral cavity into the pharynx and then to oesophagus below
• Walls of pharynx consist of 3 layers of tissue
1. The lining membrane (mucosa)
2. The middle layer – fibrous tissue
3. The outer layer –involuntary muscles
28
Pharynx
• Lined with stratified squamous epithelium
• Pharyngeal muscles assist in swallowing– Pharyngeal constrictor muscles– Palatal muscles
Esophagus
• 25cm long
• 2cm in dia
• Front of vertebral column
• Behind the trachea
• Continuous with pharynx
• Joints the stomach
29
30
Esophagus• Compressed form -arch of aorta - left brochi - left attrium• Surrounded by
– SNS plexus– Blood vessels
• Functions– Secrete mucous– Transport food
No chemical digestion occurs in the esophagus.
The entrance of the esophagus to the stomach is marked by a constriction, called a SPHINCTER;
----the sphincter must relax in order for food to enter the stomach.
The sphincter prevents food from backing up into the esophagus.
31
32
- four layers of tissue
-Adventia layer consist of elastic fibrous tissue
Attaches the oesophagus to the surrounding structures
Bolus formation• Bolus formed is pushed into pharynx (by
action of voluntary muscles of tongue and cheeks
• Muscles of pharynx contract n propels the bolus-----to esophagus -- stomach
• Epiglottis prevents entry into trachea
33
Formation of bolus
34
35
Stomach
• Usually “J” shaped• Left side, anterior to the spleen• Mucous membrane
– G cells – make gastrin– Goblet cells – make mucous– Gastric pit – Oxyntic gland – Parietal cells – Make
HCl– Chief cells – Zymogenic cells
• Pepsin• Gastric lipase
36
37
Anatomy of the Stomach
38
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
39
Gastric Juice
40
obesity
41
42
43
44
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
45
Small Intestine
46
Small Intestine
• Histology– Intestinal glands – Intestinal enzymes– Duodenal glands – Alkaline mucous– Paneth cells – Lysozyme– Microvilli– Lacteals– Plica circularis– Smooth muscle– Lymphatic tissue – GALT– Vascular
47
48
Small Intestine
• Absorbs– 80% ingested water– Electrolytes– Vitamins– Minerals– Carbonates
• Active/facilitated transport
• Monosaccharides
– Proteins• Di-/tripeptides• Amino acids
– Lipids• Monoglycerides
• Fatty acids
• Micelles
• Chylomicrons
49
Structure of the Villi in the Small Intestine
50
51
Small Intestine
• Secretes digestive enzymes– Peptidases– Sucrases– Maltase– Lactase– Saccharidases
• Di-• Tri-
– Lipase– Nucleases
52
Small Intestine
• Requires pancreatic enzymes & bile to complete digestion
• Overview of digestive system
• Layers of digestive tract
• Structure of mouth
• Teeth
• Tougue
• Salivary glands
• Pharynx
• Oesophagus
• stomach
• Small intestines
• Large intestines
• Pancreas
• Liver
• Gall bladder
• Rectum,anal cannal
• Digestion and absorbtion of nutrients
53
Absorption of nutrients in SI
• Diffusion
• Active transport: FASTER
monosaccharides ,a.a,fatty acids intestinal lumen villi capillaries
54
55
Large Intestine
56
Large Intestine
• 1.5meters long,width= 6.5cm• Extends from ileocaecal valve to anus• Regions
– Caecum –– Colon
• Ascending
• Transverse
• Descending,sigmoid
– Rectum– Anal canal
Layers
• 4 layers
• Mucosa: goblet cells ------more
• Submucosa: ----more lymphoid tissue
• Muscularis---longitudinal----3bands---taenia coli
57
58
Anatomy of the Large Intestine
59
functions• Absorption
• Immunity
• Mass movement(MM) and defecation
• Intestine distend
•
MM increased
• Send efferent impulses
60
• Afferent impulses relax the internal sphincter
• defecation occurs
• (can be controlled voluntarity by external sphincter
61
• Commensals-- non pathogenic bacteria lines intestine
• prevents harmful bacteria to attach n invade intestine
• Synthesis of vitamin K--PREVENT BLEEDING
62
functions
• ABSORPTION\
• IMMUNITY
• COMMENSALS: SYSTHESIS OF VITAMIN K
• MASS MOVEMENT
• DEFECATION
63
• Intestine distend
• mass movement gastrocolic reflex
• send efferent impulses to higher centers
• afferent impulses
•
64
• relax internal anal sphincter
• defecation reflex occurs
•
• controlled by voluntarity by external anal sphincter
65
Difference
Large I SMALL I
LENGTH 1.5m 6m
width 6.5cm 2.5cm
parts colon Duodeum,jejunum,ilieum
haustrations + -
Taenia coli 3 0
Fat epiploic appendages + -
region retroperitoneal intraperitoneal
66
ANAL CANAL
• Two sphincter muscles control the anus
67
Internal external--Smooth muscle ---skeletal muscle--autonomic nerves --voluntary controlsystem
68
69
70
Large Intestine
• Histology– No villi– No permanent circular folds– Smooth muscle
• Taeniae coli
• Haustra
– Epiploic appendages– Otherwise like rest of Gl tract
71
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
72
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
73
Pancreas
• Intraabdominal /retroperitoneal
• 60grams
• 12-15cm
• Situation: epigastrium,umbilical,left hypochondriac regoin
74
75
Endocrinal (islet cells)
Alpha beta delta gamma-glucagon insulin somatostatin pancreatic polypeptide
- reduce the rate at --which reduces appetite
which food is
absorbed
76
Exocrine (Acinar cells)
• Secrete Pancreatic Juice
-water, mineral salts,enzymes
-Proteins:trypisinogen,chymotrypsinogen
Carbohydrate: pancreatic amylase
lipids: pancreatic lipase
77
78
Liver
79
Liver
• Location– R. Hypochondrium– Epigastric region
• Lobes– Left and Right-----functionally– Quadrate– Caudate anatomically
• Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein
80
81
82
83
84
R.Atrium of heart
• IVC
• blood leavin liver
hepatic vein
• •
• central vein
• • sinusoid blood in liver
•
• Interlobular vein
85Portal veins-de oxygenated blood
Functions--Metabolism
- carbohydrate
-fats
-proteins
--Synthesis of plasma proteins
--Defense against microbes
--Detoxification of drugs
--Inactivation of hormones
86
87
Gall Bladder
CARBOHYDRATE METABOLISM
• Glycogenesis(excess glucose)
• Glycogenolysis(low glucose)
• Glyconeogenesis(when glycogen stores are low)
88
89
Liver
• Functions– Makes bile
• Detergent – emulsifies fats• Release promoted by:
– Vagus n.– CCK– Secretin
• Contains– Water– Bile salts– Bile pigments– Electrolytes– Cholesterol– Lecithin
90
Liver– Detoxifies/removes
• Drugs• Alcohol
– Stores• Gycolgen• Vitamins (A, D, E, K)• Fe and other minerals• Cholesterol
– Activates vitamin D– Fetal RBC production– Phagocytosis
Gall bladder
• Pear shaped
• Attached to posterior surface of liver
• Parts
• fundus
• body
• neck
• 4 layers
91
• Blood supply
• hepatic artery
•
• cystic artery
• blood to GB
• Drained by cystic vein +portal vein
92
functions
• Reservoir of bile
• Release of bile when stimulated by hormones cholecystokinin and secreatin
93
Bile
• Secreted by liver
• Ph ; 8,100-500ml
• Greyish green
• Composition
water,mineral salts,bile salts,bile pigments,cholesterol
94
95
The Organs and Positions in the Abdominal Cavity