Transcript Digestive System

Chapter
17
D- Digestive system
Anatomy and Physiology
17-1
Chapter 17
Digestive System
Functions of Digestive System
• ingestion
• mechanical digestion
• chemical digestion
• propulsion
• absorption
• defecation
17-2
Major Organs
17-3
Alimentary Canal
17-4
Alimentary Canal Wall
17-5
Movements of the Tube
• mixing movements
• peristalsis
17-6
Innervation of the Tube
• submucosal plexus – controls secretions
• myenteric plexus – controls gastrointestinal motility
• parasympathetic impulses – increase activities of
digestive system
• sympathetic impulses – inhibit certain digestive actions
17-7
Mouth
• ingestion
• mechanical
digestion
• prepares food for
chemical digestion
17-8
Tongue
17-9
Palate
• roof of oral cavity
17-10
Primary Teeth
• 8 incisors
• 4 cuspids
• 8 molars
17-11
Secondary Teeth
17-12
Section of a Tooth
17-13
Salivary Glands
17-14
Secretions of Salivary Glands
• Parotid glands
• clear
• water, serous fluid
• rich in amylase
• Sublingual glands
• primarily mucus
• most viscous
• Submandibular glands
• primarily serous fluid
• some mucus
17-15
Pharynx
17-16
Swallowing Mechanism
• soft palate and uvula raise
• hyoid bone and larynx elevate
• epiglottis closes off top of trachea
• longitudinal muscles of pharynx contract
• inferior constrictor muscles relax and esophagus opens
• peristaltic waves push food through pharynx
17-17
Swallowing Mechanism
17-18
Esophagus
17-19
Stomach
17-20
Radiograph of Stomach
17-21
Descriptive terms for the peritoneum
• Mesentery- double layer of peritoneum connecting
organs with other organs or to the abdominal wall.
Mesentery contains connective tissue with
neurovascular, lymphatic vessels, and fat.
Mesentary of the large intestine is called
mesocolon.
• Omentum- double layer extension of peritoneum
• Greater- from the greater curvature of the stomach
it hangs down like a apron. After descending, it
folds back and attaches to the transverse colon.
• Lesser- connects the lesser curvature of the stomach
and the duodenum to the liver.
Arterial supply to abdominal region
Celiac- just distal to the aortic hiatus
Divides into left gastric, splenic, and common hepatic
arteries
Supplies esophagus, stomach, duodenum, liver and pancreas
Left gastric- celiac trunk – supplies the distal esophagus
and lesser curvature of the stomach.
Splenic- supplies the body of pancreas, spleen, and greater
curvature of stomach.
Left gastro-omental- origin splenic- left portion of greater
curvature of stomach
Short gastric- supplies the fundus of stomach
Arteries
Hepatic- celiac- one third of liver,
gallbladder, stomach, pancreas, duodenum,
and lobes of liver
Right gastric- hepatic- tight portion of lesser
curvature of stomach
Right gastro-omental- tight portion of
greater curvature of stomach
PhrenicSuperior mesenteric- small intestine and
ascending and transverse colon
Arteries
• Suprarenal- supplies blood to the adrenal glands
• Renal- divides into lobar branches within the kidney.
• Gonadal- Female paired arteries to ovaries.
Male- passes through the inguinal canal to supply
the testes.
• Inferior mesenteric- supplies the descending colon, sigmoid
and the rectum
• Lumbar- 3 or 4 arise from the posterior aorta to supply
muscles of the skin and posterior abdominal wall.
• Middle sacral – small- carries blood to the sacrum and
coccyx.
Lining of Stomach
17-22
Gastric Secretions
• pepsinogen
• from chief cells
• inactive form of pepsin
• pepsin
• from pepsinogen in presence of
HCl
• protein splitting enzyme
• hydrochloric acid
• from parietal cells
• needed to convert pepsinogen
to pepsin
• mucus
• from goblet cells and mucous
glands
• protective to stomach wall
• intrinsic factor
• from parietal cells
• required for vitamin B12
absorption in the small intestine
17-23
Perinicious anemia
• Autoimmune disorder
• Damage to the parietal cells fail to produce
intrinsic factor required for absorption of
Vitamin B12.
Regulation of gastric secretions
• Nervous and endocrine
• Somatostatin, which is a hormone released by
specialized cells inhibits acid secretion.
• Ach released from the parasympathetic endings
of the vagus nerve.
• Inhibits secretion of somatostatin and
stimulates gastric juice.
• Stimulates gastrin, increasing gastric secretion
and histamine release, which, in turn, causes
additional gastric secretion.
Intestinal regulation
• Intestinal hormone, gastrin enhances gastric
secretion.
• Cholecystokinin- is released in response to
proteins and fat causing decrease gastric
motility.
• Somatostatin is stimulated by fats and
inhibits release of gastric juices.
Regulation of Gastric
Secretions
17-25
Phases of Gastric Secretion
• Cephalic phase
• triggered by smell, taste, sight, or thought of food
• parasympathetic impulses trigger gastric juice secretion
• Gastric phase- 40% - 50%
• triggered by presence of food in stomach, the pH rises
• gastrin released in response to increase pH
• As the pH approaches 3 gastrin is inhibited
• Intestinal phase
• triggered by movement of food into small intestine
• intestinal cells release intestinal gastrin
• secretion of gastric juice
17-24
Gastric Absorption
• some water
• certain salts
• certain lipid-soluble drugs
• alcohol
• Most all nutrients are absorbed in the small intestine
17-26
Mixing and Emptying Actions
17-27
Enterogastric Reflex
regulates the rate at which chyme leaves the stomach
17-28
Pancreas
17-29
Pancreatic Juice
• pancreatic amylase – splits glycogen into
disaccharides
• pancreatic lipase – breaks down triglycerides
• trypsin, chymotrypsin, and carboxypeptidase –
digest proteins
• nucleases – digest nucleic acids
• bicarbonate ions – make pancreatic juice alkaline
17-30
Regulation of Pancreatic
Secretions
• acidic chyme
stimulates release of
secretin
• secretin stimulate
release of pancreatic
juice
17-31
Liver
17-32
Hepatic Lobule
17-33
The Paths of Blood and Bile in
Hepatic Lobule
17-34
Liver Functions
• produces glycogen from glucose
• breaks down glycogen into glucose
• converts noncarbohydrates to glucose
• oxidizes fatty acids
• synthesizes lipoproteins, phospholipids, and cholesterol
• converts carbohydrates and proteins into fats
• deaminates amino acids
• forms urea
• synthesizes plasma proteins
• converts some amino acids to other amino acids
• stores glycogen, vitamins A,D, B12, iron, and blood
• phagocytosis of worn out RBCs and foreign substances
• removes toxins from blood
• produces and secretes
17-35
Composition of Bile
• water
• bile salts
• emulsification of fats
• absorption of fatty acids, cholesterol, and fat-soluble
vitamins
• bile pigments
• cholesterol
• electrolytes
17-36
Gallbladder
17-37
Regulation of Bile Release
• fatty chyme entering
duodenum stimulate
gallbladder to release
bile
17-38
Three Parts of Small Intestine
17-39
Mesentery
• suspends portions of the
small intestine from the
posterior abdominal wall
17-40
Intestinal Villus
17-41
Intestinal Epithelium
17-42
Wall of Small Intestine
17-43
Secretions of Small Intestine
• peptidase – breaks down peptides into amino acids
• sucrase, maltase, lactase – break down disaccharides into
monosaccharides
• lipase – breaks down fats into fatty acids and glycerol
• enterokinase – converts trypsinogen to trypsin
• somatostatin – hormone that inhibits acid secretion by stomach
• cholecystokinin – hormone that inhibits gastric glands,
stimulates pancreas to release enzymes in pancreatic juice,
stimulates gallbladder to release bile
• secretin – stimulates pancreas to release bicarbonate ions in
pancreatic juice
17-44
Regulation of Small
Intestinal Secretions
• mucus secretion stimulated by presence of chyme in
small intestine
• distension of intestinal wall activates nerve plexuses
in wall of small intestine
• parasympathetics trigger release of intestinal
enzymes
17-45
Absorption in the
Small Intestine
• monosaccharides and
amino acids
• through facilitated
diffusion and active
transport
• absorbed into blood
• electrolytes and water
• through diffusion,
osmosis, and active
transport
• absorbed into blood
17-46
Absorption in the
Small Intestine
• fatty acids and glycerol
• several steps
• absorbed into lymph
and blood
17-47
Movements of the
Small Intestine
• mixing movements
• peristalsis – pushing movements
• segmentation – ringlike contractions
• overdistended wall triggers peristaltic rush
resulting in diarrhea
17-48
Large Intestine
17-49
Large Intestinal Wall
17-50
Functions of Large Intestine
• little or no digestive function
• absorbs water and electrolytes
• secretes mucus
• houses intestinal flora
• forms feces
• carries out defecation
17-51
Movements of Large Intestine
• slower and less frequent than those of small intestine
• mixing movements
• peristalsis
• mass movements usually follow meals
17-52
Feces
• water
• electrolytes
• mucus
• bacteria
• bile pigments altered by bacteria provide color
• smell produced by bacterial compounds
17-53
Life-Span Changes
• teeth become sensitive
• gums recede
• teeth may loosen or fall out
• heartburn more frequent
• constipation more frequent
• nutrient absorption decreases
• accessory organs age but the effects are less
noticeable
17-54
Clinical Application
Hepatitis
• inflammation of the liver
• most commonly caused by viral infection
• can be caused by reactions to drug, alcoholism or autoimmunity
Signs and Symptoms
• headache
• low fever
• fatigue
• vomiting
• rash
• foamy urine
• pale feces
• jaundice
• pain
Hepatitis A – not washing hands or
eating raw shellfish
Hepatitis B – chronic; serum
Hepatitis C – serum
Hepatitis D – very severe; only produces
symptoms if infected with B; serum
Hepatitis E, F, G – more rare
17-55