Transcript Biol 155 Human Physiology

Phases of Gastric Secretion
Stomach Histology
• Rugae: Folds in
stomach when empty
• Gastric pits: Openings
for gastric glands
– Contain cells
• Surface mucous: Mucus
• Mucous neck: Mucus
• Parietal: Hydrochloric
acid and intrinsic factor
• Chief: Pepsinogen
• Endocrine: Regulatory
hormones
Hydrochloric Acid Production
Movements in Stomach
Small Intestine
• Site of greatest amount of
digestion and absorption
• Divisions
– Duodenum
– Jejunum
– Ileum: Peyer’s patches or
lymph nodules
• Modifications
– Circular folds or plicae
circulares, villi, lacteal,
microvilli
• Cells of mucosa
– Absorptive, goblet, granular,
endocrine
Movement in small intestine:
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Mixing: Segmental contraction that occurs in small intestine
Secretion: Lubricate, liquefy, digest
Digestion: Mechanical and chemical
Absorption: Movement from tract into circulation or lymph
Elimination: Waste products removed from body
Small Intestine Secretions
• Mucus
– Protects against digestive enzymes and stomach acids
• Digestive enzymes
– Disaccharidases: Break down disaccharides to
monosaccharides
– Peptidases: Hydrolyze peptide bonds
– Nucleases: Break down nucleic acids
• Duodenal glands
– Stimulated by vagus nerve, secretin, chemical or tactile
irritation of duodenal mucosa
Duodenum and Pancreas
Duodenum Anatomy and Histology
Liver
• Lobes
– Major: Left and right
– Minor: Caudate and
quadrate
• Ducts
– Common hepatic
– Cystic
• From gallbladder
– Common bile
• Joins pancreatic duct at
hepatopancreatic ampulla
Blood and Bile Flow
Duct System
Gallbladder
• Bile is stored and concentrated
• Stimulated by cholecystokinin and vagal
stimulation
• Dumps into small intestine
• Production of gallstones possible
– Drastic dieting with rapid weight loss
Pancreas
• Anatomy
– Endocrine
• Pancreatic islets produce
insulin and glucagon
– Exocrine
• Acini produce digestive
enzymes
– Regions: Head, body, tail
• Secretions
– Pancreatic juice
(exocrine)
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Trypsin
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Pancreatic lipases
Enzymes that reduce DNA
and ribonucleic acid
Bicarbonate Ion Production
Gastric hormones:
Liver Histology
portal
triad
Figure 24.20a, b
3. Architecture of the Hepatic
Parenchyma
The hepatic lobule is the structural unit of the liver.
Portal vein
Bile duct
Sinusoids
Central vein
Portal area
Hepatic artery
Liver cells (Hepatocytes)
Bile
…each day around 600 ml of bile is produced…
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Bile acid
Phospholipids
Cholesterol
Bilirubin
Waste products
Electrolytes
Mucin
Functions of the Liver
• Bile production
– Salts emulsify fats, contain pigments as bilirubin
• Storage
– Glycogen, fat, vitamins, copper and iron; huge blood reservoir of blood
(storage); very high lymph flow
• Nutrient interconversion – Metabolic functions (see next
slide)
• Detoxification
– Hepatocytes remove ammonia and convert to urea; metabolizes drugs,
hormones; has the Cytochrome P-450 enzyme system.
• Phagocytosis – Cleans the blood
– Kupffer cells phagocytize worn-out and dying red and white blood cells,
some bacteria
• Synthesis
– Albumins, fibrinogen, globulins, heparin, clotting factors
Liver’s Role in Metabolism
Carbohydrate Metabolism
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Storage of large amounts of glycogen
Conversion of galactose and fructose to glucose
Gluconeogenesis
Formation of many chemical compounds from intermediate
products of carbohydrate metabolism
Fat Metabolism
• Beta-oxidation of fatty acids to supply energy to for other
functions in the body
• Synthesis of cholesterol, phospholipids, and most lipoproteins
(and their receptors)
• Synthesis of fats from proteins and carbohydrates
Liver’s Role in Metabolism (cont’d)
Protein Metabolism
• Deamination of amino acids
• Formation of urea for removal of ammonia from the body
fluids
• Formation of plasma proteins
• Interconversion of the various amino acids and synthesis of
other compounds from amino acids
Exocrine Pancreas –
Enzymes
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Trypsinogen
Chymotrysinogen
Carboxypeptidases
Pro-elastase
Phospholipase
pancreatic lipase
Pancreatic amylase
Bicarbonate Ion Production
Lipoproteins
• Types
– Chylomicrons
• Enter lymph
– VLDL
– LDL
• Transports cholesterol
to cells
– HDL
• Transports cholesterol
from cells to liver
Water and Ions:
• Water
– Can move in either direction
across wall of small intestine
depending on osmotic
gradients
• Ions
– Sodium, potassium, calcium,
magnesium, phosphate are
actively transported
Large Intestine:
• Extends from ileocecal junction to anus
• Consists of cecum, colon, rectum, anal canal
• Movements sluggish (18-24 hours)
Large Intestine
• Cecum
– Blind sac, vermiform appendix attached
• Colon
– Ascending, transverse, descending, sigmoid
• Rectum
– Straight muscular tube
• Anal canal
– Internal anal sphincter (smooth muscle)
– External anal sphincter (skeletal muscle)
– Hemorrhoids: Vein enlargement or inflammation
Secretions of Large Intestine
• Mucus provides protection
– Parasympathetic stimulation increases rate of
goblet cell secretion
• Pumps
– Exchange of bicarbonate ions for chloride ions
– Exchange of sodium ions for hydrogen ions
• Bacterial actions produce gases called flatus
Histology of Large Intestine
Movement in Large Intestine
• Mass movements
– Common after meals
• Local reflexes in enteric plexus
– Gastrocolic: Initiated by stomach
– Duodenocolic: Initiated by duodenum
• Defecation reflex
– Distension of the rectal wall by feces
• Defecation
– Usually accompanied by voluntary movements to expel feces
through abdominal cavity pressure caused by inspiration
Reflexes in
Colon and
Rectum:
Digestion, Absorption, Transport
• Digestion
– Breakdown of food molecules for absorption
into circulation
• Mechanical: Breaks large food particles to small
• Chemical: Breaking of covalent bonds by digestive
enzymes
• Absorption and transport
– Molecules are moved out of digestive tract and
into circulation for distribution throughout body
Effects of Aging
• Death of myenteric plexus neurons
• Atrophy of sphincter muscles
Incontinence
• Decrease in mucus layer, connective tissue,
muscles and secretions
• Increased susceptibility to infections and toxic
agents
– Ulcerations and cancers