Download Digestive System: What you need to know!!!!! Structures: a. mouth

Digestive System: What you need to know!!!!!
Structures:
a. mouth teeth
a. pancreas
b. salivary glands
b. gall bladder c. colon
c. esophagus
d. liver
d. small intestine
e. rectum
e. stomach
Functions:
Main region for enzymatic digestion and nutrient absorption
Consolidation of the feces before elimination
Main function is water and mineral absorption
Secretes acid and pepsin, stores and mixes food
A gland which produces an alkaline, enzyme-rich fluid
Produces bile and has many homeostatic functions
Produces saliva which contains the enzyme amylase
The two major roles of nutrients in the diet are energy source and raw materials for metabolism,
growth, and repair of cells
The “New Food Pyramid”- distinguish between healthy and unhealthy types of carbohydrates and fats
The consumption of plant oils which are unsaturated are recommended over other fats because of the
direct correlation of heart disease with saturated fats
Vegans must consider the source of Vitamin B, A, and amino acids that may be absent from the food
they eat while avoiding animal products
Digestion begins in the mouth with the introduction of enzymes and saliva during mastication.
The epiglottis prevents food from going into the trachea and directs it toward the esophagus
The role of the tonsil is to provide immune protection from pharyngeal and upper respiratory tract
infection
The hypothalamus regulates eating.
How does a bolus of food move through a tube gut? Peristalsis, circular muscles contract behind the
bolus pushing it forward while the longitudinal muscles in front contract shortening the tube and
widening it at the same time.
The tube gut of the human is regionalized to help make it more efficient
Bulky, low energy diets of processed foods, requires a larger longer gut to accommodate the volume of
food. This increases the time food spends in the gut and can lead to toxicity and constipation within the
colon.
Mastication physically breaks down food by increasing surface area and allowing enzymes to work
Absorption allows products of chemical digestion to enter the bloodstream, and water and salts to be
reabsorbed to prevent dehydration.
Peristalsis or gut movement moves food through gut and mixes the food so it is accessible to digestive
enzymes and lubricating mucus
Small molecules like glucose, aspirin, and alcohol are absolved directly across the stomach wall into the
gastric blood vessels surrounding the stomach.
Bile is produced by liver cells, stored in the gall bladder and released via the bile duct into the
duodenum
Bile is a watery, alkaline fluid that neutralizes stomach acids and maintains the correct pH for enzymatic
activity
Bile also contains bile salts which emulsify large fat droplets, increasing the surface area for the action of
lipase enzymes
Chyme is the soupy mixture of food and gastric secretions in the stomach
The pancreas is both endocrine – producing insulin hormone that regulates blood sugar levels in the
blood, and exocrine – secreting pancreatic juice via the pancreatic duct to the duodenum
Most nutrients are absorbed in the small intestine, the remaining fluid pass into the large intestine
whose main function is to reabsorb water and electrolytes.
Infection viral or bacterial, or disease can cause an increase in gut movement and insufficient
reabsorption of water and diarrhea.
Sluggish gut movement may cause the reabsorption of too much water and the feces become hard and
difficult to pass, a condition known as constipation.
Egestion of feces is controlled by two sphincters in the anus, one voluntary and the other under
involuntary reflex control.
Large intestine contains crypts, tubular glands, goblet cells, that produce mucus which lubricate the
colon wall and aids in the formation of feces.
Appendicitis is the obstruction of the appendix by fecal matter or some other cause leading to an
inflammation, it can develop rapidly 6-12 hours causing severe abdominal pain and nausea, vomiting,
and fever. When severe it can be life threatening, and is treated by surgical removal of appendix called
an appendectomy.
The Hepatic Portal System or the blood flow into and out of the Liver is separate from the regular
circulatory system.
The liver receives deoxygenated blood via the hepatic portal vein directly from the small intestine, this
blood is nutrient-rich and the nutrients are delivered to the liver for storage and processing and then the
blood moves to the heart
The liver receives oxygenated blood via the hepatic artery to exchange gasses etc… just like other
organs.
Lipids are absorbed differently than other nutrients. The epithelial cells receive the lipids and process
them into triglycerides and then package them into aggregates called micelles which are further
packaged and coated with protein to keep them in suspension while they travel via the lymphatic
system to the heart to be introduced to the regular circulatory system.
The majority of digestive juices are secreated only when there is food in the gut and both nervous and
hormonal mechanisms are involved in coordinating and regulating this activity.
The digestive system is innervated by branches of the autonomic nervous system (sympathetic and
parasympathetic stimulation).
Hormones include gastrin, secretin, and cholecystokinin released into the bloodstream in response to
nervous or chemical stimuli and influence the activity of gut and associated organs.
Salivation is secreted continuously in response to parasympathetic stimulation via the vagus nerve, the
presence of food in the mouth stimulates the salivary glands and stomach to increase secretions.
Smell, sight, and thought of food also stimulates secretion, this involves higher brain activity and
learning, a conditioning reflex.
Presence of fat and acid in small intestine stimulates release of bile and intestinal mucosa
The presence of food in the stomach causes it to stretch, this mechanical stimulus results in secretion of
gastrin and the simple reflex of motility “churning”
The primary functions of the liver metabolizes fats, carbohydrates, and amino acids (glucose to glycogen
and amino acids to urea), 2nd stores iron, copper, and vitamins
ORS or oral rehydration solutions are used to treat dehydration due to infection or disease.
Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerea.
The Vibrio bacteria produces an enterotoxin which binds to membrane receptors on the small intestine,
opening the ion channels and increasing permeability of mucosal epithelium to cholorine ions, and
water follows salts across a membrane. So watery diarrhea results.
Prolong diarrhea leads to severe dehydration kidney failure and death with hours if left untreated.
Chloera can be prevented when human feces is disposed of properly and safe drinking water is available,
safe food preparation and effective hygiene are essential
ORS prevent dehydration and can be administered intravenously in severe cases.
Diarrhea causes water and electrolytes to be lost from the body, this effects hydration, blood pH, nerve
and muscle function. Water alone can not treat dehydration. ORS contain salts, glucose and sucrose.
Obesity is a form of malnutrition, due to overconsumption of food, often processed and high fat diet
Body Mass Index or BMI of 30+ indicates mild obesity, morbid obesity is 40+
Simple explanation for excessive body fat is” energy in exceeds energy out,” but it is a complex
biological and socio-economic factors are implicated in creating the problems with modern obesity.
Malnutrition is nutritional deficiencies
Starvation is not enough food in general, regardless of nutritional value
Scurvy lack of Vitamin C
Rickets lack of Vitamin D
Pernicious anemia lack of vitamin B12
Anemia lack of iron
Vitamin A deficiency = loss of night vision, inflammation of eye, corneal damage
Vitamin C deficiency= Scurvy disturbs the body’s normal production of collagen a protein in connective
tissue that holds body structures together. Results in poor wound healing rupture of small blood vessels
swollen gums and loose teeth.
Vitamin B12 required for nucleic acid and protein metabolism and the maturation of red blood cells.
Essential for proper growth and for proper nervous system function defieciency results in anemia poor
appetite weight loss growth failure fatigue brain damage nervousness muscle tics depression spinal cord
degeneration and lack of balance.
Lack of vitamin D causes rickets which results in skeletal deformities because inadequate amounts of
phosphorus and calcium are incorporated into the bones. Vitamin D is produced by the skin when
exposed to sunlight and it is vital for the absorption of calcium from the diet.
Iodine is essential for the production of thyroid hormones which control growth metabolic rate and
development. Shortage of iodine in the diet may lead to goiter an enlargement of the thyroid gland
Iron – anemia results from lower than normal levels of hemoglobin in the Red blood cells, iron from the
diet is required to produce hemoglobin. Lack of hemoglobin = reduction in Oxygen efficiency
Zinc- important for enzyme activity, including the production of insulin, making of sperm and perception
of taste. A deficiency causes growth retardation a delay in puberty muscular weakness dry skin and a
delay in wound healing.
Calcium is required for enzyme function, formation of bones, and teeth, blood clotting, and muscle
contraction. Deficiency causes fragile bones, loss of teeth, muscular spasms, and poor blood clotting.
Excessive alcohol consumption can cause nutritional deficiencies: damage to the gastrointestal tract,
inflammation and ulceration of the stomach lining, reduced peristalsis and pancreatic secretion,
decreased digestion and absorption of nutrients including fats, proteins, and vitamins
Diabetes Type 1 :absolute deficiency of insulin (not produced) pancreas no longer functions, treatment
insulin replacement
Type 2: the inability of the body cells to recognize insulin produced by the pancreas, treatment dietary,
exercise, anti-diabetic drugs, and insulin therapy, often the result of being overweight and the stress of
excessive fat on the organs