• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/283

Click to flip

283 Cards in this Set

  • Front
  • Back
True or False: All tissues are bathed by blood which contains hormone.
False - not the brain or placenta
What is the advantage of most tissues being bathed by blood which contains hormone?
allows body to adjust to changing conditions and function synchronously
True or False: Hormones can be released in response to nerve stimulation.
True
What is the purpose of an immunoassay?
recognizes a single hormone
What enzymes are activated by cAMP?
adenylyl cyclase
protein kinase A
What is cAMP made from?
ATP
What does diacylglycerol activate?
protein kinase C
What is the effect of inositol triphosphate?
triggers release of Ca2+ from endoplasmic reticulum
What triggers release of Ca2+ from the endoplasmic reticulum?
inositol triphosphate
What activates protein kinase C?
diacylglycerol
What enzyme catalyzes the conversion of phosphatidylinositol 4,5-diphosphate to inositol 1,4,5-triphosphate and diacylglycerol?
phospholipase C
What reaction is catalyzed by phospholipase C?
conversion of phosphatidylinositol 4,5-diphosphate to inositol 1,4,5-triphosphate and diacylglycerol
What activates adenylyl cyclase and protein kinase A?
cAMP
What are the three regions of the pituitary gland?
anterior lobe - adenohypophysis
posterior lobe - neurohypophysis
intermediate lobe - pars intermedia
Which hormones are produced by the anterior lobe of the pituitary gland?
FSH - follicle stimulating hormone
LH - luteinizing hormone
ACTH - adrenocorticotropic hormone
GH - growth hormone
TSH - thyroid stimulating hormone
PRL - prolactin
Which gland produces the following hormones: FSH, LH, ACTH, GH, TSH, PRL?
pituitary gland (anterior lobe)
True or False: Growth hormone directly stimulates growth.
False - IGF-I stimulates growth
Where are GHRH and somatostatin produced?
hypothalamus
What is the function of somatostatin?
inhibits release of growth hormone, insulin, and glucagon
What inhibits release of growth hormone from the pituitary gland?
somatostatin
What promotes release of growth hormone from the pituitary gland?
growth hormone releasing hormone (GHRH)
Growth hormone increases the activity of what kind of cells?
chondrocytes
What kinds of extrinsic factors affect growth?
protein
vitamins
minerals
calories
True or False: GH fails to promote growth in absence of insulin or thyroid hormones.
True
What are the three phases of growth?
in utero
prepubertal
puberty
Which phase of growth is primarily due to GH?
prepubertal
What is involved in growth during the in utero phase?
IGF-I and IGF-II
What is involved in growth during the prepubertal phase?
GH and thyroid hormones
What hormone is involved in growth during puberty?
testosterone or estrogen
What causes growth to cease during puberty?
estrogen
In what age range does IGF-I peak?
13-17
What causes linear growth to stop?
closure of the epiphyses of long bones
True or False: Growth hormone is important in adults.
True
True or False: GH plasma levels are low during the first days of life and increase by about 2 weeks of age.
False
When in the day do growth hormone levels peak?
shortly after the onset of sleep
What activites cause an increase in the level of growth hormone?
exercise
eating
fasting
What are the physiological effects of GH on proteins?
increases amino acid transport into cells (positive nitrogen balance)
increases mRNA (and protein) synthesis
What are the physiological effects of GH on fatty acids?
increases release from adipose tissues (and blood lipid levels)
increases usage of fatty acids as energy source
ketosis from prolonged GH excess
What are the physiological effects of GH on carbohydrates?
decreases utilization by inhibiting glucose uptake into muscle
increases tissue glycogen stores
increases blood carbohydrate levels
True or False: Pituitary diabetes severely affects glucose utilization.
False - only moderate effect
True or False: Prolonged elevation of blood glucose can lead to true diabetes.
True - due to burn out of insulin producing cells of the pancreas
True or False: IGF-I has direct effect on linear growth.
True
What disease states are caused by excess growth hormone?
gigantism in growing person
acromegaly if linear growth has stopped
What is acromegaly?
excess growth of soft tissues due to excess growth hormone
What disease state is caused by growth hormone deficiency?
dwarfism
What disease state is caused by IGF-I deficiency?
Laron dwarfism
True or False: Laron dwarfism cannot be treated with growth hormone.
True
Laron dwarfism is caused by deficiency of which hormone?
IGF-I
Is growth hormone deficiency a primary or secondary growth abnormality?
secondary
Is osterochondrodysplasia a primary or secondary growth abnormality?
primary
What is caused by excess ACTH?
Addisons and Cushing syndromes and skin darkening
Which hormones are released from the intermediate lobe of the pituitary gland?
MSH - melanocyte stimulating hormone
αMSH has the same first thirteen amino acids as which other hormone?
ACTH
Which hormones are released from the posterior lobe of the pituitary gland?
ADH - antidiuretic hormone
oxytocin
Where are ADH and oxytocin produced?
hypothalamus
(ADH in supraoptic nuclei)
(oxytocin in paraventicular nuclei)
Which gland releases melanocyte stimulating hormone?
pituitary gland (intermediate lobe)
How are ADH and oxytocin transported from the hypothalamus to the posterior lobe of the pituitary gland?
along axons of the neurohypophyseal tract
What is the effect of ADH on the kindeys?
increased water reabsorption due to increased permeability of collecting ducts
What is caused by a lack of ADH?
diabetes insipidus - excretion of large volumes of urine
What is caused by a lack of insulin?
diabetes mellitus
Dilute urine is associated with which type of diabetes?
diabetes insipidus
Sweet urine is associated with which type of diabetes?
diabetes mellitus
What are some factors that can increase release of ADH from the posterior lobe of the pituitary gland?
surgical stress
morphine
nicotine
barbiturates
What is the threshold of plasma osmolarity for the release of ADH from the posterior lobe of the pituitary gland?
280 mOsm
What is the normal plasma osmolarity?
290 mOsm
What are some factors that can decrease release of ADH from the posterior lobe of the pituitary gland?
alcohol
opiate antagonists
What is caused by massive amounts of ADH?
hemmorhage or circulatory shock due to contraction of smooth muscles of blood vessels (increases blood pressure)
What are the effects of oxytocin?
contraction of smooth muscle of the uterus (parturition) and myoepithelial cells of the breasts (milk letdown effect)
True or False: Oxytocin causes milk to be ejected into the ducts of the breasts.
True
Which gland produces calcitonin?
thyroid gland (C-cells)
Which hormone is produced by the C-cells (parafollicular cells) of the thyroid gland?
calcitonin
True or False: Calcitonin is a thyroid hormone.
False - peptide hormone
Where in the thyroid gland is thyroglobulin located?
colloid (middle of all of the follicles)
Where is iodide absorbed?
intestine
What is the minimum daily requirement of iodide?
75 µg
How much iodide is in a typical daily diet in the U.S.?
300-400 µg
What are the four classes of cell membrane hormone receptors?
G protein coupled
tyrosine kinase
cytokine
TGF-β
Is iodide taken up by the cells of the thyroid gland by active transport or passive diffusion?
active transport
How many times greater can iodide concentration be in the cells of the thyroid gland compared to the blood?
25-50
What do G protein coupled receptors activate?
adenylyl cyclase (ATP --> cAMP)
True or False: Thyroglobulin is a glycoprotein.
True
True or False: Under normal circumstances, there is a limited store of colloid in the thyroid gland.
False - normally a vast store
What is a goiter?
enlarged thyroid gland
What is the function of thiocyanates and perchlorate?
block uptake of iodide
What is the function of propylthiouracil and methimazole?
block organification and coupling of iodide
What are thiocyanates, perchlorate, propylthiouracil, and methimazole known as?
goitrogens
What is the name of the enzyme that deiodinates monoiodotyrosine and diiodityrosine?
iodotyrosine dehalogenase
Which is secreted from the thyroid gland in higher amounts: T3 or T4?
T4
True or False: The vast majority of T3 and T4 are covalently bound to specific circulating proteins.
False - noncovalently bound
What proteins do T3 and T4 bind to?
thyroxine binding globulin (TBG)
thyroxine binding prealbumin (TBPA)
albumin
True or False: T4 is converted to T3 in peripheral tissues.
True
True or False: If synthesis of thyroid hormone were to suddenly stop, there would be rapid changes in thyroid hormone levels.
False
Which hormones control thyroid hormone secretion?
thyrotropin-releasing hormone (TRH)
thyroid stimulating hormone (TSH)
T3 & T4
What is thyrotropin-releasing hormone (TRH) released from?
hypothalamus
What is the effect of thyrotropin-releasing hormone (TRH)?
stimulates release of thyroid stimulating hormone (TSH) from the anterior lobe of the pituitary glamd
What processes does thyroid stimulating hormone (TSH) stimulate?
iodide uptake
organification of iodide
coupling of iodide
thyroglobulin breakdown
Which subunit is the same for TSH, FSH, LH, and LCG?
α-subunit
Do T3 & T4 inhibit or stimulate release of TSH from the anterior lobe of the pituitary gland?
inhibit
What can result from an absence of T3 & T4?
goiter
Does increased iodide cause a decrease or increase in responsiveness to TSH?
decrease
Does decreased iodide cause a decrease or increase in responsiveness to TSH?
increase
What is the most common form of hyperthyroidism?
Graves disease
Which hormone is found in most cases of Graves disease?
long acting thyroid stimulator (LATS)
What disease is caused by absence of thyroid hormones?
cretinism
Do thyroid hormones lead to decreased or increased O2 consumption by almost all body tissues?
increased
Do low amounts of thyroid hormones cause an increase in protein breakdown or synthesis?
increase in protein synthesis
Do excessive amounts of thyroid hormone cause an increase in protein breakdown or synthesis?
increase in protein breakdown
Does hyperthyroidism cause a decrease or increase in heart rate?
increase
Does hypothyroidism cause a decrease or increase in heart rate?
decrease
What is myxedema and what is it caused by?
puffiness of skin due to increased water retention caused by low levels of thyroid hormones
True or False: Thyroid hormones decrease sensitivity of heart to catecholamines.
False - increase sensitivity
What are poor toleration of cold, coarse fair, husky & low voice, and slow mental processes characteristic of?
severe myxedema from hypothyroidism
True or False: TSH levels are elevated in hypothyroidism.
True - due to loss of feedback inhibition
How can cretinism be treated?
thyroid hormone replacement
What are the characteristics of cretinism?
dwarfed, mentally retarded children
What are hear intolerance, nervousness, and exophtalamus characteristic of?
hyperthyroidism
True or False: Thyroid gland tumors are associated with goiters.
False
True or False: Graves disease is associated with goiter.
True
What percentage of the pancreas is made up of Islets of Langerhans?
1-2%
What do the α cells of the pancreas secrete?
glucagon
Are the α cells of the pancreas responsible for an anabolic or catabolic effect?
catabolic
Which pancreatic cells secrete glucagon?
α cells
What percentage of pancreatic cells are α cells?
25%
What is secreted by the β cells of the pancreas?
insulin
Are the β cells of the pancreas responsible for an anabolic or catabolic effect?
anabolic
What percentage of pacreatic cells are β cells?
60%
What is secreted by the δ cells of the pancreas?
somatostatin
What is secreted by the F cells of the pancreas?
pancreatic polypeptide
True or False: Glucagon, somatostatin, and pancreatic polypeptide are only secreted by cells of the pancreas?
False - also by cells in mucosa of GI tract
What type of hormone is insulin?
polypeptide hormone
What is the structure of insulin?
A and B chains connected by disulfide bonds
What percentage of the population has diabetes mellitus?
5%
Which chain in insulin is longer: A chain or B chain?
B chain
Is juvenile onset diabetes a type 1 or type 2 diabetes?
type 1
True or False: There is a strong genetic link for type 2 diabetes?
True
At what age does type 2 diabetes generally occur?
after 40
True or False: Type 2 diabetes can often be controlled with diet.
True
What does hyperglycemia refer to?
elevated plasma glucose levels because glucose uptake by many tissues is decreased
What is the normal plasma glucose level?
90 mg%
What is the normal blood glucose level in urine?
0
What does glycosurea refer to?
capacity of kidneys to reabsorb glucose is exceeded
What does polyurea refer to?
high osmolarity due to glucose draws in water causing increased urine flow
What does ketosis refer to?
increased protein and fat catabolism due to low intracellular glucose levels
What can ketosis lead to if left untreated?
acidosis and coma
What does polydipsia refer to?
excessive thirst
What does polyphagia refer to?
increased appetite with weight loss
What are 7 characteristics of diabetes mellitus?
hyperglycemia
glycosurea
polyurea
ketosis
polydipsia
polyphagia
reduced growth
Which enzyme in the liver is induced by insulin?
glucokinase (catalyzes glucose --> glucose-6-P)
True or False: Insulin increases the number of glucose transporters in the cell membrane of liver cells.
False
What are some tissues that are not affected by insulin?
intestine
kidneys
brain
red blood cells
True or False: Oral glucose and intravenous glucose promote insulin release with the same effectiveness.
False - oral glucose is more effective
What happens in the two phases of the effect of glucose?
First Phase: insulin peaks within 5 minutes due to release of existing stores
Second Phase: due to synthesis of insulin
What is the effect of the drug metformin?
stimulates sensitivity to insulin
Prolonged stimulation by glucose can lead to hypertrophy and exhaustion of which cells of the pancreas?
β cells
Which cells in the gut secrete glucose-dependent insulinotropic peptide (GIP)?
K cells
Which cells in the gut secrete glucagon-like peptide-1 (GLP-1)?
L cells
What are the two incretins from the gut that are responsible for oral glucose being more effective than intravenous glucose in promoting insulin release?
glucose-dependent insulinotropic peptide (GIP)
glucagon-like peptide-1 (GLP-1)
True or False: Amino acids and β-keto acids cause insulin release.
True
Does glucagon lower or raise blood glucose levels?
raise
What kind of hormone is glucagon?
polypeptide hormone
True or False: Elevated blood glucose levels alone can cause a decrease in glucagon secretion.
False - some insulin must be present
Which gene in the Y chromosome is the sex-determining region?
SRY gene
True or False: Genetic sex is determined at the time the egg is fertilized by the sperm.
True
What are the accessory sex tissues in males?
epididymus
vas deferens
seminal vesicles
ejaculatory duct
What are the accessory sex tissues in females?
uterus
fallopian tubes
What is a Barr body?
the inactive X chromosome in somatic cells of a female
True or False: An embryo at the seventh week of intrauterine life is equppied with the primordia of both the male and female genital ducts.
True
Which ducts develop into the accessory sex tissues in females?
mullerian ducts
Which ducts develop into the accessory sex tissues in males?
Wolffian ducts
Do the mullerian ducts develop into the accessory sex tissues in females or males?
females
Do the Wolffian ducts develop into the accessory sex tissues in females or males?
males
What factors lead to development of the male accessory sex tissues?
androgens and mullerian inhibiting factor from the fetal testis
What makes up 80% of the testes?
seminiferous tubules
What do the seminiferous tubules of the testes drain into?
epididymis
How much is the difference in temperature in the scrotum compared to the body core?
1-2ºC lower
What percentage of the testes are made up of seminiferous tubules?
80%
What are the two types of cells in the testis?
Sertoli cells
Leydig (interstitial) cells
Which cells of the testis act as a source of nourishment for spermatids?
Sertoli cells
Which cells of the testis extend from the basement membrane to the lumen of the seminiferous tubule?
Sertoli cells
What is the function of the Sertoli cells of the testis?
act as a source of nourishment for spermatids
Where in the testis are the Sertoli cells located?
extending from the basement membrane to the lumen of the seminiferous tubule
Where in the testis are the Leydig cells located?
between the seminiferous tubules
Which cells of the testis are the major source of androgens?
Leydig cells
What is the major androgen produced by the Leydig cells of the testis?
testosterone
Which cells of the testis are located between the seminiferous tubules?
Leydig cells
What is the function of the Leydig cells of the testis?
major source of androgens
True or False: The prepubertal testis produces extremely low levels of testosterone.
True
What is the testosterone level in adult males?
600 ng/dL
What are three forms of testosterone in the body?
1-2% free form
65% noncovalently bound to sex steroid-binding globulin
33% bound to albumin & other proteins
At approximately what age does the lumen of the seminiferous tubules develop and spermatogenesis begin in males?
12
True or False: In a prepubertal male, the seminiferous tubules contain spermatogonia and Sertoli cells.
True (but they are solid - no lumen)
Approximately how many sperm are produced by a male each day?
100-200 million
Describe spermatogenesis up to the development of spermatozoa.
- spermatogonia undergo mitosis to produce primary spermatocytes
- primary spermatocytes undergo meiosis to produce secondary spermatocytes
- secondary spermatocytes undergo meiosis to produce spermatids
- spermatids lose cytoplasm, form a tail, and develop into spermatozoa
True or False: As spermatozoa develop, they are displaced away from the lumen of the testes.
False
Describe the flow of sperm from the testes out the urethra.
- sperm drain from the seminiferous tubules into the epididymis
- sperm move to the vas deferens
- sperm move through the ejaculatory ducts
- sperm move into the urethra in the body of the prostate
How long after ejaculation do sperm remain active?
about 2 days
How long after ejaculation do sperm become capacitated?
4-6 hours
How many sperm are there in the typical 2-4 mL ejaculate?
200-400 million
How long does it take for spermatids to develop from spermatocytes?
60-70 days
True or False: Certain hormones affect the rate of the development of spermatocytes.
False
How long does it take for sperm to move through the epididymis?
2-4 weeks
What is the function of the epididymis?
allows for the maturation of sperm
What is the function of the vas deferens?
storage site for sperm
True or False: Sperm may remain viable in the vas deferens for several months.
True
Which structure is the storage site for sperm?
vas deferens
Which structure allows for the maturation of sperm?
epididymis
True or False: Testosterone is an anabolic steroid.
True
What is caused by premature secretion of testosterone?
shortened stature due to premature uniting of the epiphysis of long bones
True or False: Testosterone causes a decrease in the bone matrix, leading to bone thinning.
False
Testosterone increases retention of which elements?
nitrogen
potassium
phosphorus
calcium
What is the effect of leutenizing hormone (LH) on the testes?
acts on Leydig cells to promote testosterone synthesis
Where is gonadotropin releasing hormone (GnRH) released from?
hypothalamus
What is the effect of gonadotropin releasing hormone (GnRH) on the testes?
stimulates fetal secretion of testosterone
Which hormone promotes the synthesis of testosterone by the Leydig cells of the testes?
leutenizing hormone (LH)
Which hormone stimulates fetal secretion of testosterone?
gonadotropin releasing hormone (GnRH)
What is the effect of follicle stimulating hormone (FSH) on the testes?
acts on Sertoli cells and is required for proper spermatogenesis
Which hormone acts on the Sertoli cells of the seminiferous tubules and is required for proper spermatogenesis?
follicle stimulating hormone (FSH)
True or False: Testosterone depresses hypothalamic release of gonadotropin releasing hormone (GnRH).
True
What are some causes of hypogonadism?
lack of functional testis
lack of LH or FSH secretion
cryptorchidism (undescended testes)
castration
What is the effect of hypogonadism on growth and muscle?
increase in height and weaker muscles
True or False: Hypogonadism developing after puberty will cause the accessory sex glands to decrease in size.
True
What is secreted by the outer cortex of the adrenal gland?
cortisol
aldosterone
weak androgens
What is secreted by the inner medulla of the adrenal gland?
epinephrine
norepinephrine
dopamine
What part of the adrenal gland produces steroids?
outer cortex
Which part of the adrenal gland produces catecholamines?
inner medulla
What are the three zones of the adrenal cortex (from outer to inner) and what is secreted from each zone?
zona glomerulosa - aldosterone
zona fasciculata - cortisol
zona reticularis - cortisol
What is the most important mineralocorticoid?
aldosterone
Where do mineralocorticoids promote sodium reabsorption?
kidney (distal & collecting tubules, part of loop of Henle)
sweat glands
salivary glands
intestinal glands
Do mineralocorticoids decrease or increase Cl reabsorption?
increase
Do mineralocorticoids decrease or increase H excretion?
increase
Do mineralocorticoids decrease or increase K excretion?
increase
True or False: Hypoaldosteronism can result in death if untreated.
True
What is the effect of hypoaldosteronism?
decreased cardiac output and shock-like state
True or False: In hypoaldosteronism, Na reabsorption decreases in the kidney and there is a decrease in extracellular fluid volume.
True
What is the effect of hyperaldosteronism?
increased cardiac output and hypertension
What system controls aldosterone secretion?
renin-angiotensin system
True or False: A decrease in K concentration leads to an increase in aldosterone secretion.
False
True or False: An increase in K concentration leads to an increase in aldosterone secretion.
True
True or False: A decrease in Na concentration leads to an increase in aldosterone secretion.
True
True or False: An increase in Na concentration leads to an increase in aldosterone secretion.
False
What is the function of renin?
cleaves angiotensinpgen to produce angiotensin I
Where in the body does angiotensin-converting enzyme act to convert angiotensin I to angiotensin II?
lungs
What does angiotensin II cause?
release of aldosterone
What are ACE inhibitors used as a treatment for?
heart failure
What results from an absence of cortisol?
impaired metabolic function
impaired ability to withstand physical stress
True or False: Glucocorticoids cause an increase in the rate of gluconeogenesis in the liver.
True
Do glucocorticoids cause a decrease or increase in blood glucose levels?
increase
Do glucocorticoids cause a decrease or increase in protein catabolism in most tissues?
increase
True or False: Glucocorticoids cause an increase in protein catabolism in the liver.
False
Do glucocorticoids cause a decrease or increase in fatty acid mobilization?
increase
True or False: Glucocorticoids have a stimulatory effect on inflammatory and allergic reactions.
False
Do glucocorticoids inhibit or stimulate secretion of corticotopin releasing hormone (CRH) and adenocorticotopin (ACTH)?
inhibit
What is the main form of glucocorticoids in the blood?
noncovalently bound to corticoid binding globulin (CBG)
Does stress inhibit or stimulate the release of glucocorticoids?
stimulate
When in the day are glucocorticoid plasma levels the highest?
shortly before waking up
When in the day are glucocorticoid plasma levels the lowest?
start of the sleep cycle
Is Addisons Disease a condition of hyperadrenalism or hypoadrenalism?
hypoadrenalism
Is Cushings Disease a condition of hyperadrenalism or hypoadrenalism?
hyperadrenalism
What are the effects of the loss of glucocorticoids?
loss of ability to regulate blood glucose levels
ACTH levels rise due to loss of feedback control
skin darkening
What are the effects of having excess glucocorticoids?
elevated blood glucose (can lead to diabetes mellitus)
bone & muscle weakness due to extrahapatic breakdown of protein
True or False: Cushings Disease can cause masculinization in females.
True
What kind of cells make up the adrenal medulla?
modified ganglion cells
Which hormones are catecholamines?
epinephrine
norepinephrine
Is the secretion of catecholamines from the adrenal medulla controlled by the parasympathetic or sympathetic nervous system?
sympathetic
Describe the flow of catecholamine formation.
tyrosine --> 3,4-dihydroxyphenylalanine --> dopamine -->
norepinephrine --> epinephrine
Does norepinephrine act preferentially through α receptors or β receptors?
α receptors
Does epinephrine act preferentially through α receptors or β receptors?
β receptors
What are some things increased by cathecholamines?
liver glycogenolysis
blood glucose
blood lactate
plasma potassium
plasma free fatty acids
ability to handle emergency situations
Which hormone is formed by hydroxylation of vitamin D3?
1,25-dihydrocholecalciferol
What is the normal plasma calcium level?
9-11 mg%
What are the three forms of plasma calcium?
ionized (50%)
bound to serum proteins (40%)
unionized (10%)
What is the effect of low plasma calcium?
increased permeability of neuronal membrane causing tetany
What is the effect of high plasma calcium?
sluggish reflex activity of central nervous system
What is the annual turnover of bone calcium in adults?
18%
What is the annual turnover of bone calcium in infants?
100%
What is the function of calcium salts in bone?
compressional strength
What is the function of the organic matrix in bone?
tensile strength
Is there more organic matrix or salts in bone?
salts (75%)
What is the primary component of the organic matrix in bone?
collagen (97%)
What is the function of calcium salts in bone?
compressional strength
What is the function of the organic matrix in bone?
tensile strength
Is there more organic matrix or salts in bone?
salts (75%)
What is the primary component of the organic matrix in bone?
collagen (97%)