Endocrine glands are ductless glands that secrete hormones.
Hormones are chemical messengers that travel through the blood and change the behavior of cells.
Glands included in the endocrine system:
the pineal, hypothalamus, pituitary, thyroid, parathyroids, thymus, pancreas, adrenals, ovaries, and testes.
4 General Characteristics of hormones:
They work through receptors, many are regulated by negative feedback, some are cyclic, & hormones affect other hormones.
How do hormones work through receptors?
A receptor is a protein in a cell membrane that binds specifically to a hormone. Because hormones must bind to a specific receptor, hormones can travel through the blood and affect only certain cells.
What is negative feedback? Give an example of negative feedback using a hormone.
Negative feedback is a continuous, self- regulating process that regulates hormone levels. For instance, if thyroid hormone levels drop, the pituitary releases a hormone that stimulates the thyroid to release more thyroid hormone.
What are cyclic hormones?
hormones released in daily cycles
When are hormones associated with stress highest?
in the morning
When are growth hormone and melatonin levels highest?
When do estrogen and progesterone levels rise and fall?
during the menstrual cycle
How do hormones affect other hormones? Give an example.
One hormone may up regulate another by increasing the number of receptors. For example, during the menstrual cycle, estrogen increases progesterone receptors.
What are the two structural types of hormones?
Peptide hormones & protein hormones
What structural hormone type is the most common type?
What are steroid hormones based on?
Name 2 steroid hormones:
sex hormones & adrenal hormones
What is the process that peptide hormones use to communicate?
Signal transduction is the process by which peptide hormones communicate with a cell.
What are the 5 steps of signal transduction?
Binding of the hormone to its specific receptor. Activation of a G protein. Activation of a membrane enzyme. Production of a second messenger. A series of reactions that will vary depending on the cell type. For instance, the series of reactions might end with release of glucose from a liver cell.
Because an enzyme is involved in signal transduction, a very tiny amount of hormone can have a profound effect. Hormones are very potent chemicals. The effect of a peptide hormone lasts until an enzyme breaks down the second messenger. What is this effect called?
What do steroid hormones work by?
They work by affecting gene expression
Where do steroid hormones bind to a receptor and act as transcription factors?
in the cell cytoplasm or in the nucleus
Why does a transcription factor interact with DNA?
to increase transcription (production) of a particular mRNA. The code on the mRNA is then used to translate a protein.
What is a peptide hormone that affects gene expression?
Location of the pineal gland?
The pineal gland is located in the roof of the third ventricle.
What does the pineal gland secrete?
The pineal gland secretes melatonin. Melatonin is a hormone that is released in daily cycles. Levels of melatonin are highest at bedtime and cause drowsiness.
What does melatonin from the pineal gland inhibit?
Melatonin from the pineal inhibits sexual development. If the pineal gland is destroyed, onset of puberty will be premature.
What gland responds to the pineal gland?
Since the hypothalamus has receptors for melatonin, what does melatonin probably affect?
Melatonin probably affects other daily cycles such as variations in body temperature that are under control of the hypothalamus.
Location of the hypothalamus?
The hypothalamus is between the thalamus and the pituitary.
What is the hypothalamus called the master endocrine gland?
Because it secretes releasing and inhibiting hormones that control the pituitary. For instance, for growth hormone, the hypothalamus makes both GHRH (growth hormone releasing hormone) and GHIH (growth hormone inhibiting hormone).
Location of the pituitary?
The pituitary is inferior to the hypothalamus and connected to it by the infundibulum.
Do the anterior and the posterior pituitary have the same embryonic origins?
What is another name for the anterior pituitary?
What type of cells are the cells in the anterior pituitary?
What is another name for the posterior pituitary?
What type of tissue does the posterior pituitary begin as?
neural embryonic tissue
What is the purpose of the posterior pituitary?
Storage. Some hormones made in the hypothalamus are transported along microtubules to the neurohypophysis which stores and releases them as needed. No hormones are made in the neurohypophysis.
Name the 2 ways Growth Hormone releases energy?
Growth hormone releases energy by stimulating release of glucose from glycogen stored in the liver. Growth hormone stimulates use of fat reserves for energy.
What is glycogen?
a chain of glucose molecules
Name 3 anabolic effects of Growth Hormone?
Growth hormone stimulates cells to increase in size and divide. Growth hormone increases protein production by cells. IGF is insulin-like growth factor. To increase protein production, growth hormone works with IGF to increase uptake of amino acids.
What is gigantism?
Gigantism is hypersecretion of growth hormone before adult height is attained.
What is acromegaly?
Acromegaly is hypersecretion of growth hormone after adult height is attained.
What happens in acromegaly?
The jaw, hands and feet enlarge in acromegaly because these bones retain the ability to respond to growth hormone.
What is pituitary dwarfism caused by?
Pituitary dwarfism is caused by abnormally low levels of growth hormone during growth. In pituitary dwarfism, body proportions may be normal.
In Laron syndrome, what do the recessive genes limit?
Growth. In Laron syndrome normal or even excess amounts of growth hormone are secreted, but the receptor for growth hormone is abnormal.
What are tropic hormones? Name the trophic hormones of the anterior pituitary.
Tropic hormones are hormones that affect the secretion of other hormones. TSH, ACTH, and the gonadotropins FSH and LH are all tropic hormones of the anterior pituitary.
What is TSH? What does it do?
TSH is thyroid stimulating hormone, a hormone that stimulates the thyroid to secrete thyroxine, thyroid hormone.
What does ACTH signal?
ACTH signals release of hormones of the adrenal cortex, especially the glucocorticoids during stress.
What are the two Gonadotropins? What do they affect?
FSH & LH. The ovary & testes.
What is FSH? What is it necessary for?
FSH is follicle stimulating hormone. FSH is necessary for gametes (eggs and sperm) to begin development.
What is LH? What is it necessary for?
LH is luteinizing hormone. LH is necessary for gametes to complete maturation.
What does prolactin do?
Prolactin stimulates milk production in women.
When do prolactin levels increase in women?
Near the end of pregnancy.
When does prolactin do in men?
increase testosterone levels
What is ADH?
What is ADH also called?
vasopressin or AVP (arginine vasopressin)
What are the functions of ADH?
ADH increases return of water to the blood at the kidneys. At high levels of secretion, ADH is also a vasoconstrictor.
What is hyposecretion of ADH?
What can trauma to the hypothalamus cause?
Symptoms of Diabetes insipidus?
The decrease in water returned to the blood means more is released in urine so polyuria is a symptom of diabetes insipidus.
How does a patient with Diabetes insipidus say hydrated?
Normally, someone with diabetes insipidus can compensate by drinking more water, but an unconscious, head trauma patient may become dehydrated.
How does alcohol effect ADH secretion?
Alcohol inhibits ADH secretion. The dehydration associated with alcohol consumption is due to the reduced ADH.
What is oxytocin?
Oxytocin is the other hormone produced by the hypothalamus that is stored in the posterior pituitary.
How does oxytocin play a role in childbirth?
When labor begins, increases in oxytocin released from the posterior pituitary stimulate the uterus to contract. When the uterus contracts, it stimulates release of more oxytocin. This positive feedback cycle of release of oxytocin and uterine contractions continues until the baby is born.
Why is oxytocin called the cuddle hormone?
In men and women oxytocin levels increase with the pleasureable feelings from touching - kissing, hugging, sexual arousal and orgasm.
What is TH? What does it affect?
Thyroid hormone. It affects most cells of the body.
Where is the thyroid located?
on the anterior trachea
What is the effect of TH?
The effect of TH is to increase metabolic rate. TH increases enzymes that extract energy from glucose by increasing gene expression for these enzymes. That is, TH increases metabolic rate by adding fuel to the fire (metabolic reactions).
What hormone is necessary for fetal development?
What does the thyroid store?
The thyroid stores precursor for TH called thyroglobulin colloid. This precursor is stored in the thyroid in capsule-like structures called follicles.
How is TH made?
Cells of the thyroid import iodine. Either one or two iodine molecules are bonded to an amino acid in the thyroglobulin colloid. These amino acids are combined to make either T3 or T4.
What is T4?
T4 is thyroxine, the most common form and the one measured to determine levels of TH in the blood.
What is T3?
T3 is the more active form and most of T3 is produced at target organs.
Symptoms of hypothyroidism?
Symptoms include coarse hair and skin, pale, lethargy and dulled mental function, feeling cold, low heart rate and blood pressure, weight gain, and constipation.
Symptoms of hyperthyroidism?
Symptoms include fine hair and skin, flushed, agitated and nervous, feeling hot, rapid, irregular heart rate and high blood pressure, weight loss and diarrhea.
What are the 2 types of hypothyroidism?
Goiter & Cretinism
What is a cause of Goiter?
Low levels of iodine in the diet cause goiter. Because TH is low, TSH stimulates the thyroid constantly and the thyroid responds by making and storing more thyroglobulin colloid.
Where was Goiter once common?
Goiter was once common where iodine was not readily available, for instance in the Midwest. The Midwest of the U.S. was once called the goiter belt because soils were low in iodine, iodine-rich seafood was not readily available, and salt was not iodized.
What is the cause of cretinism?
Low levels of iodine during fetal development and infancy cause a condition called cretinism.
What are the effects of cretinism?
Effects of cretinism include severe mental retardation and malformation of the skeleton.
What is Grave's disease?
Grave's disease is the most common hyperthyroidism. Grave's disease is an immune disease where an antibody mimics thyroid stimulating hormone.
The thyroid also make calcitonin. What is it? What does it do?
Calcitonin is the antagonist of parathyroid hormone. Calcitonin decreases blood levels of calcium by stimulating uptake of calcium by bone cells.
Function of PTH?
Parathyroid hormone raises blood levels of calcium.
What is the affect PTH has on osteoclasts and the kidneys?
PTH affects osteoclasts and the kidneys. PTH activates osteoclasts, the cells that dissolve bone matrix to release calcium to the blood. PTH increases return of calcium to the blood at the kidneys.
Effect PTH has on vitamin D?
PTH increases the amount of vitamin D precursor (made in the skin) that is activated at the kidneys. Vitamin D increases calcium absorption by cells of the small intestine.
Location of the adrenals?
The adrenals are enclosed in a capsule that sits atop the kidneys.
What is the structure of the adrenals?
The outer layers of the adrenals are called the cortex and the central region is called the medulla.
How many layers does the adrenal cortex have?
There are three layers of the adrenal cortex. Each layer produces mainly one type of adrenal hormone.
What are mineralocorticoids produced by?
the outer layer of the adrenal cortex
What is the main mineralocorticoid?
What does Aldosterone do?
it acts at the kidneys and increases return of sodium to the blood
What is Addison's disease?
Addison's disease is an autoimmune disease that affects the adrenals and decreases secretion of aldosterone. Low aldosterone levels cause low levels of sodium in the blood.
What are symptoms of Addison's disease?
Abnormal bronzing of the skin, dehydration, and low blood pressure are symptoms of Addison's.
What do glucocorticoids increase?
When are glucocorticoids levels highest?
Glucocorticoids are cyclic and levels are highest in the morning, but they also increase in the presence of stress. Stress includes any physiological stress such as hunger, cold, or blood loss as well as emotional stress.
Cortisol and cortisone are among the glucocorticoids. What do they inhibit?
Both cortisol and cortisone inhibit the immune system and inflammation.
What is Cushing's syndrome caused by?
Cushing's syndrome is caused by excess glucocorticoid, especially cortisol and cortisone. Cushing's is often from long-term use of steroids such as cortisone for inflammatory diseases.
What is Cushing's syndrome characterized by?
Cushing's is characterized by a moon face from edema, a buffalo hump of fat, brittle bones, and infections that are far advanced before symptoms appear (because of suppression of the immune system).
Describe gonadocorticoids. Who are they made in?
Gonadocorticoids are mainly androgens, but the adrenals also make small amounts of estrogen. Gonadocorticoids are made by both men and women. In women, the androgens are converted to estrogen.
When do gonadocorticoids increase?
Gonadocorticoids increase at puberty. Increasing levels of gonadocorticoids from the adrenal cortex may initiate puberty.
What can the effects be in hypersecretion of gonadocorticoids?
The effects of excess androgens is masked by testosterone in men, but in women the excess androgens cause masculinization such as growing a beard.
What is the adrenal medulla?
The adrenal medulla is an extension of the sympathetic nervous system.
What are the effects of epinephrine?
Epinephrine, commonly called adrenaline, increases heart rate, blood supply to skeletal muscles, and the strength of muscles. Epinephrine produces the fight or flight response.
What is an effect of norepinephrine?
Norepinephrine is an important vasoconstrictor.
Location of the pancreas?
The pancreas is mainly in the upper left quadrant of the abdominopelvic cavity and deep to the stomach.
What are the main targets of the pancreas?
The main targets of the pancreas are skeletal muscle and adipose tissue. The brain and kidney have no receptors for insulin, but can obtain glucose directly from the blood.
What are antagonistic hormones?
hormones that have opposite effects
Where does the pancreas secrete 2 antagonistic hormones?
from the Isle of Langerhans
What 2 types of cells are in the Isle of Langerhans?
alpha & beta
What do alpha cells secrete?
What do beta cells secrete?
What is an effect of insulin?
Insulin decreases blood glucose.
How does insulin work?
Insulin encourages storing glucose as glycogen or as fat. Insulin inhibits gluconeogenesis - making glucose from amino acids and fatty acids.
What is an effect of glucagon?
Glucagon increases blood glucose. Glucagon encourages release of glucose from the liver and gluconeogenesis.
Which diabetes is described as juvenile onset diabetes?
Diabetes Mellitus Type 1
Which diabetes is describes as adult onset diabetes?
Diabetes Mellitus Type 2. But it is frequency in the very young, especially at puberty, has increased with obesity rates.
How are insulin levels in Type 1 diabetes mellitus?
In Type I diabetes mellitus, insulin levels are low or absent.
Cause of Type 1 diabetes mellitus?
Type I is an autoimmune disease where the immune system destroys the beta cells of the pancreas.
How are insulin levels in Type 2 diabetes mellitus?
In Type II diabetes, insulin is produced, but its effect is inadequate.
Causes of Type 2 diabetes in obese?
Adipose tissue secretes resistin which decreases sensitivity to insulin Resistin may have a role in diabetes mellitus Type II.
Causes of Type 2 diabetes in pregnant women?
Type II sometimes appears during pregnancy because the pancreas must increase in size to meet the needs of both the mother and baby. In obesity also, the pancreas must serve more cells.
Symptoms of diabetes mellitus are the 3 P's:
Polydipsi, Polyphagia, & Polyuria
What is polydipsia?
What is polyphagia?
What is polyuria?
What is ketoacidosis in diabetes mellitus?
Ketoacidosis is accumulation of acids from excess use of fatty acids for energy as the body attempts to compensate for the lack of access to glucose.
What is a hormone that the heart secretes? What does it do?
Atria of the heart secrete atrial natriuretic peptide which lowers blood pressure by inhibiting aldosterone.
What is a hormone that the kidney secretes? What does it do?
The kidney produces renin which raises blood pressure. The kidney produces EPO, erythropoietin which increases production of red blood cells.`
What is leptin?
Adipose tissue produces leptin which decreases appetite and helps to maintain weight.
Adipose tissue secretes two hormones that affect insulin. Name them and their effect.
One, adiponectin, increases sensitivity to insulin and another, resistin, decreases sensitivity to insulin.
What is an antigen?
An antigen is anything that the immune system recognizes as foreign, but antigens are frequently proteins.
What are antibodies?
Antibodies are proteins made by cells of the immune system that cause clumping and lysing of antigens.
What are preformed antibodies for blood types?
Preformed antibodies for blood types are antibodies that are present in your blood before you have been exposed to their specific antigen.
How will an immune response involving preformed antibodies be?
It will be much faster and stronger.
What do the blood types A, B, AB, and O refer to?
Blood types A, B, AB, and O refer to proteins in the cell membrane of red blood cells.
What is RH?
Rh is another protein in RBC membranes. Someone who is Rh positive has the Rh protein and someone who is Rh negative lacks this protein. Rh protein does not cause a serious immune reaction on the first exposure.
What happens when someone lack A or B proteins?
They make preformed antibodies to these proteins.
What could happen from a mistransfusion of A or B?
A mistransfusion of A or B is potentially lethal due to the presence of these preformed antibodies.
What is a mistransfusion?
receiving the wrong type of blood
What happens to a person when they receive a mistransfusion?
Receiving the wrong type of blood causes clumping and lysing of erythrocytes, poor circulation, and release of toxic iron from lysed erythrocytes. Kidney failure and multiple organ failure may occur.
Why is Type O the universal donor?
Other blood types do not make preformed antibodies to type O so it is the universal donor.
Why is AB the universal receiver?
AB has neither A nor B preformed antibodies so it is the universal receiver.
There are preformed antibodies to A and B in type O. (INFO CARD)
Notice that when O is used as a donor for another blood type such as A or B, the O blood will have preformed antibodies to A and B, but only a limited number. Transfusion of type O to other blood types is possible, but not ideal.
What is an autologous transfusion?
a transfusion of your own blood or a perfect match
What could happen in the first pregnancy if the mother is Rh negative and the father Rh positive?
If the mother is Rh negative and the baby is Rh positive, the mother may form antibodies to Rh factor during delivery when the placenta tears away and some of mother's blood comes into contact with Rh positive blood of the baby.
What could happen in the subsequent pregnancy if the mother is Rh negative and the father Rh positive?
Rh positive offspring are at risk because the mother's antibodies may enter the baby's bloodstream, causing a condition called erythroblastosis fetalis.
What is erythroblastosis fetalis?
Erythroblastosis fetalis means the mother's antibodies cross the placenta and attack the baby's blood.
What is RhoGAM and what is it given for?
RhoGAM contains antibodies to Rh. These are given late in a first pregnancy to prevent formation of antibodies by the mother.
Blood composition by percentages:
RBC 45% Plasma 54% Buffy Coat 1%
What are is another name for RBC?
What does the buffy coat in blood consist of?
leukocytes and platelets
What is the hematocrit of blood?
The erythrocytes as a percent of blood volume, is about 45% because plasma is mostly water, hematocrit is affected by hydration.
What is the hemoglobin content of erythrocytes?
Hemoglobin content of erythrocytes is about 13-18 g/dL (grams per deciliter or one tenth of a liter)
What are the formed elements of blood?
erythrocytes, platelets, and leukocytes
Of the formed elements of blood, what are the only true cells?
What is plasma mostly made of?
What is dissolved in plasma?
nutrients, wastes, gases, and hormones
Where are transport proteins located?
What do iron and lipids travel through?
Iron and lipids travel through blood attached to special transport proteins. Iron is carried by a transport protein called transferrin.
What is albumin? What is it important for?
The most abundant protein in blood is albumin, a transport protein. Most therapeutic drugs are transported by albumin. Albumin is important for osmosis, diffusion of water into blood.
What is the shape of erythrocytes?
Erythrocytes have a flattened shape that increases the surface area for rapid diffusion of gases.
What is Spectrin?
Spectrin is a protein that makes RBCs flexible enough to squeeze through capillaries.
Do erythrocytes have organelles?
Erythrocytes lack organelles so they do not consume oxygen. A RBC (red blood cell) ejects the nucleus and mitochondria when it matures.
How long is the lifespan of an erythrocyte?
Without a nucleus RBCs, last only 3 or 4 months.
What is the structure of hemoglobin?
Hemoglobin consists of 4 peptide chains called globins and 4 heme groups. When the heme is carrying oxygen, it is bright red. Arterial blood is bright red. When the heme group is deoxygenated, it is a bluish red. Venous blood is a bluish red.
What is oxygen carried by in hemoglobin?
An iron atom in the center of each heme so each hemoglobin molecule carries 4 oxygen.
What is carbon dioxide carried by in hemoglobin?
Carbon dioxide is carried by globins. Globins carry some of the carbon dioxide that is carried in the blood.
Due to cooperativity of binding, oxygen and carbon dioxide tend to do what to hemoglobin?
Drive each other off hemoglobin. In this way, hemoglobin is able to pick up oxygen at the lungs where oxygen concentration is high, but deliver oxygen at tissues where carbon dioxide concentration is high.
What happens to erythrocytes?
They are recycled by macrophages in the liver and spleen. The iron from RBCs is stored in the liver and then released to the blood on a transport protein, transferrin.
When it is not attached to a protein, iron is what?
What is transferrin?
Iron from the heme group of old erythrocytes is attached to a protein, transferrin, in the liver. Iron travels to bone marrow on transferrin.
Macrophages convert the red heme of hemoglobin into what?
What is bilirubin?
a yellow pigment
What happens to bilirubin in blood?
Bilirubin in blood is picked up by liver cells and becomes a normal component of bile that will be excreted.
What is the hormone that the kidneys release that increases the number of red blood cells?
What does erythropoietin (EPO) do?
It acts by increasing maturation rate of erythrocytes.
What is HIF?
It is a hormone that increases the rate of EPO release. Normally, an enzyme keeps HIF levels low. In hypoxic conditions, the enzyme stops functioning and HIF levels increase.
Where do increases in the number of erythrocytes occur?
In hypoxic conditions such as high altitude or cardiovascular disease.
What is the process that stops bleeding?
What does pain from an injury cause?
Pain from an injury causes the contraction of smooth muscle in blood vessels and helps to slow blood loss.
What do platelets do to an injury?
Platelets adhere to an injury and attract more platelets by changing shape (becoming sticky like Velcro)
What releases thromboxane? What does thromboxane do?
Thromboxane is released by platelets to attract more platelets to the site of an injury.
What inhibits thromboxane?
Where are most clotting factors made? What do they require?
Most clotting factors are made in the liver and require vitamin K.
As the blood slows at the platelet plug, what happens?
Clotting factors begin to accumulate. This increase in the concentration of clotting factors is essential for a clot to form.
Once the concentration of clotting factors is high enough, what happens?
A cascade of reactions begins that will form a clot.
What does the intrinsic pathway consist of?
Reactions that would occur in a test tube. These reactions are slower and more complex than the extrinsic pathway.
What is added to stored blood to prevent clotting by the intrinsic pathway?
What type of reactions are simpler, but require the release of tissue factor by damaged tissues?
Extrinsic pathway reactions
How are the final steps of clotting the same for both pathways (extrinsic & intrinsic)?
Both pathways produce prothrombin activator which acts as a catalyst for conversion of prothrombin to thrombin. Thrombin acts as a catalyst for the reaction that changes fibrinogen to fibrin.
What is a fibrous protein that forms a net that catches red blood cells and forms the clot?
What do platelets secrete?
Platelets secrete PDGF, platelet derived growth factor, which stimulates repair of nearby tissues.
Why do platelets use contractile proteins, such as actin?
to pull nearby tissues and reduce the size of the clot.
What is serum?
Serum is plasma without the clotting proteins.
When does serum appear?
When platelets shrink a clot, serum appears around the clot.
What is the process of dissolving clots called?
What is plasminogen?
Within a clot is an inactive coagulant called plasminogen. The active form is called plasmin. Plasmin is an anticoagulant that dissolves clots.
Tissues near a clot will secrete tissue plasminogen activator. What will it do?
It will change plasminogen to its active form, plasmin.
Basophils will release heparin, what is it?
another natural anticoagulant to help dissolve the clot.
What decreases clotting because it interferes with the activity of vitamin K?
What is an increase in leukocyte count in response to inflammatory chemicals released from injured tissue?
What is diapedesis?
Neutrophils squeeze between cells of capillary walls to enter injured tissue
What is chemotaxis?
Neutrophils follow a chemical trail of inflammatory chemicals to the injured tissue
Risk factors for the formation of abnormal clots?
Risk factors for the formation of abnormal clots include abnormal roughing of the inner surface of blood vessels which may be caused by chemical toxicity and chronic infections.
What is a risk factor for abnormal clots?
Slow flow of blood from inactivity is a risk factor for abnormal clots because clotting factors are not washed away and concentration of these factors reaches threshold level for reaction and clot formation.
What is a thrombus?
a clot that develops in an unbroken blood vessel
What is an embolus?
a clot that has broken away and is traveling in the bloodstream.
What is an embolism?
is a clot that has traveled through the blood and then obstructs another blood vessel
What are anemias?
Anemias are poor oxygen-carrying capacity of the blood due to some underlying condition. Low red blood cell counts from bleeding or abnormal red blood cells can cause anemia.
What are hemorrhagic anemias due to?
Hemorrhagic anemias are due to blood loss which may be acute or chronic as from a bleeding ulcer.
What is the importance of iron in a diet?
Iron is a component of hemoglobin so there must be adequate iron in the diet.
What is the importance of B12 in a diet?
B12 is needed for normal DNA metabolism as red blood cells mature. It is normally abundant in the diet because sources include meat and dairy products.
What is dietary anemia caused by too little vitamin B12?
What is necessary for absorption of vitamin B12?
Where is intrinsic factor made?
Intrinsic factor is made in the stomach lining so loss of the stomach lining for any reason can cause pernicious anemia.
Why are the elderly more susceptible to pernicious anemia?
Stomach lining tends to thin as people age so the elderly are susceptible to pernicious anemia.
What is sickle cell anemia?
Sickle cell anemia is a condition where erythrocytes sickle due to an abnormal amino acid in two globin chains.
How do you get sickle cell anemia?
The gene for sickle cell is recessive so you must inherit copies from parents to have sickle cell anemia.
What is sickling?
In sickle cell anemia, RBC's become brittle after releasing oxygen and clog small blood vessels.
What is the sickle cell trait?
People who have one abnormal and one normal gene have sickle cell trait.
Why are people with the sickle cell trait resistant to malaria?
People with sickle cell trait are resistant to malaria because red blood cells infected with malaria parasites sickle and are destroyed by macrophages of the immune system.
How can sickling effect athletics?
Even in sickle cell trait some sickling of RBC's occurs. Usually this sickling is not enough to affect the person's health. However, when athletes are pushed to the limits of their endurance, the loss of oxygen delivery due to sickling can be dangerous.