The Swallowing Process (Fig. 3-12)
The Stomach
Lower esophageal sphincter and pyloric sphincter
Capacity of ~4 cups
Secretion of acid and enzymes
Holds food for 2-4 hours
Result in the formation of chyme
Mucus layer prevents autodigestion
Physiology of the Stomach (Fig. 3-13)
Production of Stomach Acid
Stimulated by
Gastrin
Stomach distention
Histamine
Thoughts of food (nerve input)
Food itself
Prevents autodigestion
Stop secretion when pH is ~2
Thick mucus layer
Stomach Acid
Destroys activity of protein
Converts pepsinogen to pepsin
Partially digests dietary protein
Assist in calcium absorption
Sphincters
A muscular and circular valve in the GI tract that controls the flow of food stuff
Cardiac sphincter (or esophageal sphincter)
Pyloric sphincter
Sphincter of Oddi
Ileocecal valve
Functions of the Sphincters
Prevents reflux of stomach content to cause heartburn and ulcers
Controls the amount of stomach content into the small intestine
Controls the amount of bile into the small intestine
Prevents large intestine content (bacteria) to back up into the small intestine
Physiology of the Small Intestine
The wall is folded
Villi projections are located on the folds
Absorptive cells (enterocytes) are located on the villi
Microvilli are located on the villi
Glycocalyx are located on the microvilli
Increases intestinal surface area 600 x
Intestinal Mucosa
Absorptive cells
Produced in crypts
Migration and maturation from the crypts to the tips of the villi
Degradation of cells at the tips of the villi by digestive enzymes
Newly formed cells constantly migrate to replace dying ones (< 6 days)
High turnover causes the cells to deteriorate during nutrient deficiency
The Small Intestine (Fig. 3-15)
The Small Intestine
Duodenum
~10 inches in length
Primary site of digestion
Jejunum
~4 feet in length
Some digestion
Ileum
~5 feet in length
Little digestion
Digestive Enzymes
Enzymes speed up chemical reactions
Enzymes lowers the amount of energy needed for the action to proceed
Each enzyme acts on specific substance
Enzyme release and activation is controlled by nerves and hormones
Enzymes are only released when needed
Enzyme Action (Fig. 3-14)
In the Small Intestine
Bile acid from the liver via the gallbladder
Bicarbonate ions from the pancreas
Muscle contractions to mix the food with digestive juices
Food remains 3-10 hours in the small intestine
~95% of digestion takes place here
Movement Along the Intestine
Peristalsis
A ring of contraction propelling material along the GI tract
Segmentation
A back-and-forth action that breaks apart food
Mass movement
Peristaltic wave that contracts over a large area of the large intestine to help eliminate waste
Movement (Fig. 3-17)
Site of Absorption (Fig. 3-16)
The Large Intestine
~3 1/2 feet in length
Cecum, ascending, transverse, descending and sigmoid
Little digestion occurs
Indigestible food stuff
Absorption of water, some minerals, vitamins
Formation of feces for elimination
The Liver and Gallbladder
Nutrients are released into the portal vein to the liver
Hepatic veins release nutrients to the general circulation
Production and storage of bile
Enterohepatic circulation
Unwanted substances released into the duodenum
Detoxification by the liver
Pancreas
Produces glucagon and insulin
Secretes bicarbonate and digestive enzymes
Produces glucagon and insulin
Regulator
Vagus nerve
Turns on digestive system
Secretion of GI hormones
GI Hormones
Gastrin
Secretin
Cholecystokinin
Gastric Inhibitory Peptide
Gastrin
Originated from the pyloric region of the stomach and upper duodenum
Stimulated by food, thoughts of food
Stimulates flow of stomach enzymes and HCl
Stimulates contraction of cardiac sphincter
Slows gastric emptying
Secretin
Originated from the duodenum, jejunum
Stimulated by the presence of acidic chyme and the presence of peptones in the duodenum
Stimulates the secretion of bicarbonate
Slows gastric emptying
Cholecystokinin (CCK)
Originated from the duodenum, jejunum
Stimulated by food, presence of fat and protein in the duodenum
Stimulates contraction of gallbladder and flow of bile
Stimulates the release of enzyme rich pancreatic fluids
Slows gastric emptying
Gastric Inhibitory Peptide (GIP)
Originated from the duodenum, jejunum
Stimulated by fats and protein
Inhibits the secretion of stomach acid and enzymes
Slows gastric emptying
Urinary System
Kidney
Ureter
Bladder
Urethra
The Kidney
Regulate the composition of blood and interstitial fluid
Filtration of blood
Formation of urine
Controls blood volume and pressure
Maintains the pH of the blood
Reproductive System
Male reproductive organs
Female reproductive organs
Sex hormones
Puberty and menarche
Ulcers
Helicobacter pylori
Heavy use of aspirin
Excessive acid production in the stomach
Symptoms
Pain 2 hours after eating
Treatment
Antibiotics
Antacid
Heartburn
Gastroesophageal reflux disease
Gnawing pain in the upper chest
Acid from the stomach to the esophagus
Treatment
Smaller meals
Less fatty meals
Stop smoking
Do not lie down after eating
Avoid offending foods
Constipation
Slow movement of fecal matter
Increase fluid reabsorption; hardening of the feces
Causes:
Result from ignoring normal urge
Antacids, calcium and iron supplements
Treatment
Plenty of dietary fiber and fluids
Laxatives
Hemorrhoids
Swollen veins of the rectum and anus
Causes:
Added stress and pressure to the vessels
Treatment
Check with physician
Warm compresses to reduce pain
Adequate fiber and fluid
Irritable Bowl Syndrome
Visible abdominal distension
Crohn?s disease
No cure
Eliminate specific foods
Body Cells
Forms tissues
Tissues form Organs
Organs form Systems (e.g., digestive)
Turnover
Requires energy, adenosine triphosphate
Requires nutrients
Cell Membrane
Double layered of lipid, CHO, and protein
Hydrophilic and hydrophobic ends
Controls passage of substances
Contains receptors for hormones and protein markers
Glycoproteins and glycolipids
Nutrient Absorption
Diffusion
Facilitated diffusion
Active absorption
Endocytosis
Exocytosis
Nutrient Absorption (Fig. 3-2)
Cell Structure
Nucleus
Double membrane
Contains genetic material DNA
Directs protein synthesis and cell division
Mitochondria
Major site for energy production
Synthesis of other components, nonessential amino acids
Endoplasmic reticulum - communication network
Rough endoplasmic reticulum - protein synthesis
Smooth endoplasmic reticulum -fat synthesis
The Golgi complex
Export system
Help forms other cell organelles
Lysosomes
Cell degradation system
Cytosol
Fluid within the cell
Peroxisomes
Contain enzymes for peroxide and alcohol metabolism
A Cell (Fig. 3-1)
Four Types of Tissue in the Human Body
Epithelial
lines the body surfaces
Connective
holds structure together
Muscle
for movement
Nervous
communication
Integumentary System
Skin, hair, glands, nail
Signs of clinical deficiencies
Temperature regulation
Epidermis
Dead cells
Protection from the environment
Dermis
Deeper skin
Blood vessels, glands, nerves
Skeletal System
Rigid framework
Protection and attachment sites
Hemopoiesis within the bone marrow
Hydroxyapatite deposits in the bone
Function of osteoblasts and osteoclasts
Muscular System
Smooth
Involuntary movement
Cardiac
Involuntary rhythmic contraction
Skeletal
Voluntary movement
Glycogen supply
Muscle Contraction (Fig. 3-4)
Circulatory System
Cardiovascular system
Heart and blood vessels
Systemic circuit
Pulmonary circulation
Lymphatic system
Blood
Erythrocytes
Leukocytes
Clotting factors
Plasma
Blood Circulation (Fig. 3-5)
Heart Structure
Atria
Ventricles
Aorta to the arteries to arterioles to capillaries
Returns through the veins
Movement of Materials
Extracellular fluid
Absorption by the cells
Gas exchange
Lymphatic System
Protection
Lymph nodes with WBC (leukocytes)
Immune cells (lymphocytes), phagocytes, macrophages
Passage for large particles - lacteals
Passage for bacteria, viruses, ?trash?, cancer cells
Immune System
Defense against invading pathogens
Sensitive indicator of the body?s nutritional status
Leukocytes and macrophages
Cytokines
Nonspecific Immunity
Barriers
Mucous membrane
Mucus traps invaders
Acid in the stomach
Interferons
stimulate the synthesis of antiviral proteins
Swelling and fever
Specific Immunity
Directed at specific molecules
Antibody-medicated immunity
Antigens and antibodies interaction
Immunoglobulins (B lymphocytes and antibodies)
Memory cells
Complement proteins
T-cells
Respiratory System
Exchange of gases between blood and tissues
Air enters body via the nose and mouth
Respiratory System (Fig. 3-8)
Nervous System
Regulatory system
Central Nervous System
Brain and the spinal cord
Peripheral Nervous System
Branches out to organs
Neuron
Responds to electrical and chemical signals
Neuroglia
protects the neurons and aids in their function
A Neuron (Fig. 3-9)
Sending Signals
Neurotransmitter
Adrenergic effect
Fight or flight response
Secretion of epinephrine and norepinephrine
Cholinergic effects
Secretion of acetylcholine
Transmission is dependent on nutrients supply
Importance of glucose for brain function
Endocrine System
Secretes regulatory substances (hormones)
Desire for homeostasis
Target cells with receptor proteins
Message to the DNA directly
Use of a second messenger
Digestive System
Mouth to anus
Epithelium lines the lumen
Barrier to invaders
Submucosal layer
Muscularis
Taste and smell
Digestion and the GI Tract
Mastication
Saliva
Enzymes to help breakdown simple sugars
Mucus to lubricate the food for easier swallowing
Lysozyme to kill bacteria
Tongue
Taste receptors
Enzymes to help breakdown fatty acids
