Midterm 4 - BIOL431

endocrine gland

Typically small, unimpressive, ductless structures scattered widely over body, that empty hormones into surrounding tissue fluid; associated with rich vascular and lymphatic drainage that receives hormones; hormone producing cells arranged in cords and branching networks to maximize contact with surrounding capillaries; include pituitary, thyroid, parathyroid, adrenal, and pineal

autocrines

Local, short-distance chemical messengers that exert effect on same cells that secrete them

paracrines

Local, short-distance chemical messengers that exert effect within same tissue, but on cells other than those releasing them

hormone

Chemical messenger secreted by cells into extracellular fluid; travels through blood and regulates metabolic function of other cells in body; initiates response that typically occurs after lag period of seconds or days, but response tends to be prolonged; target most cells of body with widespread and diverse effects on reproduction, growth and development, maintenance of electrolyte water and nutrient balance of blood, cellular metabolism and energy balance, and mobilization of body defenses; structure is amino acid or steroid based; release regulated by negative feedback mechanisms via humoral, neural, or hormonal stimuli

target cell

Cell that has specific receptors for specific hormone; cell whose processes can be altered by specific hormone, with precise response depending on cell type; response may be one or more of following: alteration of plasma membrane permeability or membrane potential by opening or closing ion channels, synthesis of enzymes and other proteins, activation or deactivation of enzymes, secretory activity, or mitosis

second messenger

Intracellular molecule generated when hormone binds to receptor on plasma membrane; mechanism for connecting hormone receptor binding with intracellular machinery needed for hormone action; mechanism of water-soluble hormones, such as amino-acid based, that cannot enter cells

cyclic AMP

Intracellular second messenger that mediates effects of hormone, which is first, extracellular messenger; formed from ATP by plasma membrane enzyme adenylate cyclase; free to diffuse about cell, triggering cascade of various chemical reactions by activating protein kinases; persists only briefly in cell because its rapidly degraded by intracellular enzyme phosphodiesterase; utilized by catecholamines, ACTH, LH, glucagon, PTH, TSH, and calcitonin

G protein

Mobile, plasma membrane-bound molecule that relays signals between extracellular first messenger hormone and intracellular second messenger via an effector enzyme; may activate or inhibit effector enzyme, depending on type; activated as guanosine diphosphate bound to it is displaced by high-energy compound guanosine triphosphate; behaves like light switch: off when GDP is bound, and on when GTP is bound

protein kinase

Enzyme that phosphorylates, adds a phosphate group to, various proteins, many of which are other enzymes; activates some proteins and inhibits others, therefore may affect variety of processes in same target cell at same time; different versions exist in different target cells; component of second messenger signaling mechanisms

diacylglycerol (DAG)

Second messenger that mediates effects of hormone, which is first, extracellular messenger; one of two molecules formed from phosphatidyl inositol bisphosphate, PIP₂, by plasma membrane enzyme phospholipase C; triggers cascade of various chemical reactions by activating protein kinases; utilized by catecholamines, TRH, ADH, LHRH, and oxytocin

inositol triphosphate (IP3)

Intracellular second messenger that mediates effects of hormone, which is first, extracellular messenger; one of two molecules formed from phosphatidyl inositol bisphosphate, PIP₂, by plasma membrane enzyme phospholipase C; free to diffuse about cell, triggering

release of Ca⁺ from intracellular storage sites, with Ca⁺ becoming another second messenger; utilized by catecholamines, TRH, ADH, LHRH, and oxytocin

calmodulin

Intracellular regulatory protein that binds Ca⁺; part of PIP₂-Calcium signaling mechanism; activates enzymes that amplify cellular response

up-regulation

Persistently low levels of hormone cause its target cell to form additional receptors for that hormone; sensitizes target cell to respond more vigorously

down-regulation

Prolonged exposure to high levels of hormone cause its target cell to decrease receptors for that hormone; desensitizes target cell so it responds less vigorously, preventing overreacting

half-life

Length of time for hormone's blood level to decrease by half; varies from fraction of minute to week, with that of water-soluble hormones being shortest; influenced by rate of hormone release and speed of inactivation or removal from body

prohormone

Large precursor hormone

gigantism

Result of hypersecretion of GH during childhood because epiphyseal plates still active; person becomes abnormally tall, often reaching height of 8 ft., but has relatively normal body proportions; hypersecretion usually results from anterior pituitary tumor that churns out excessive GH; treatment is surgical removal of tumor, but does not reverse anatomical changes that have already occurred

acromegaly

Result of hypersecretion of GH after epiphyseal plates have closed; characterized by overgrowth of bony areas still responsive to GH, including bones of hands, feet, and face; treatment is surgical removal of tumor, but does not reverse anatomical changes that have already occurred

pituitary dwarfism

Hyposecretion of GH during childhood slows long bone growth; individuals attain maximum height of 4 ft., but usually have fairly normal body proportions; often accompanied by deficiencies of other anterior pituitary hormones; if diagnosed before puberty, GH replacement therapy can promote nearly normal growth

galactorrhea

Inappropriate milk production, in either females or males; due to hyperprolactinemia, most frequent abnormality of pituitary tumors

myxedema

Full-blown hypothyroid syndrome; symptoms include low metabolic rate, feeling chilled, constipation, thick dry skin and puffy eyes, edema, lethargy, and mental sluggishness; reversed with iodine supplements or hormone replacement therapy, depending on cause

endemic goiter

Enlarged protruding thyroid gland due to lack of iodine; common in areas with iodine-poor soil and no access to iodine-rich seafood; follicular cells produced thyroid follicular cells produce colloid but cannot iodinate it and make functional hormones; pituitary gland secretes increasing amounts of TSH in futile attempt to stimulate thyroid to produce TH, but only result is that follicles accumulate more and more unusable colloid

cretinism

Severe hypothyroidism in infants; child has mental disabilities, short disproportionately sized body, and thick tongue and neck; may reflect genetic deficiency of fetal thyroid gland or maternal factors such as lack of dietary iodine; prevented by thyroid hormone replacement therapy is diagnosed early enough, but developmental abnormalities and mental disabilities are not reversible one they appear

Grave's disease

Most common hyperthyroid pathology; autoimmune condition; person makes abnormal antibodies directed against thyroid follicular cells; rather than marking these cells for destruction, they mimic TSH and stimulate TH release; typical symptoms include elevated metabolic rate, sweating, rapid irregular heart beat, nervousness, and weight loss despite adequate food; eyeballs may protrude if tissue be behind eyes becomes edematous and fibrous; treatments include surgically removing thyroid gland or ingesting radioactive iodine which destroys thyroid cells that are most active

aldosteronism

Hypersecretion of aldosterone; results from adrenal tumors; hypertension and edema due to excess Na⁺ and water retention; accelerated excretion of potassium ions, and if extreme neurons become nonresponsive, leading to muscle weakness and eventually paralysis

Addison's disease

Major hyposecretory disorder of adrenal cortex; usually involves deficits in both glucocorticoids and mineralocorticoids; person loses weight, plasma glucose and sodium levels drop, and potassium

Cushing's disease

Pathology of glucocorticoid excess; may be caused by ACTH-releasing anterior pituitary tumor, an ACTH-releasing malignancy of the lungs, pancreas, or kidneys, or by tumor of adrenal cortex; most often results from clinical administration of glucocorticoid drugs; characterized by persistent elevated glucose levels known as steroid diabetes, dramatic losses in muscle and bone protein, and water and salt retention leading to hypertension and edema; signs include swollen moon face, redistribution of fat to abdomen and posterior of neck causing buffalo hump, easy bruising and poor wound healing; because of enhanced anti-inflammatory effects, infections may become overwhelmingly severe before producing recognizable symptoms; only treatment is to remove cause by surgically removing tumor or discontinuing drug

andrenogenital syndrome

Masculinization caused by hypersecretion of gonadocorticoids; in prepuberal males reproductive organs mature and secondary sex characteristics appear early, and sex drive emerges with vengeance; females develop beard and masculine distribution of body hair, and clitoris grows to resemble small penis

hirsutism

Excessive hair growth; usually refers to phenomenon in women and reflects excessive androgen production

psychosocial dwarfism

Shortened stature and failure to thrive resulting from stress and emotional disorders that suppress hypothalamic release of growth hormone-releasing hormone and thus anterior pituitary secretion of growth hormone

thyroid crisis

Sudden and dangerous increase in all manifestations of hyperthyroidism due to excessive amounts of circulating TH; signs include fever, rapid heart rate, high blood pressure, dehydration, nervousness, and tremors; precipitating factors include severe infection, excessive intake of TH supplements, or trauma

pituitary gland

Hypophysis; pea-sized structure seated in sella turcica of sphenoid bone and connected to hypothalamus superiorly via infundibulum; two major lobes, one neural tissue and other glandular

neurohypophysis

Posterior lobe of pituitary and infundibulum; composed largely of neural tissue such as pituicytes, glial-like support cells, and nerve fibers; consists largely of axon terminals of hypothalamic neurons; releases neurohormones received ready-made by hypothalamus, therefore hormone storage area rather than endocrine gland that manufactures hormones; stores ADH and oxytocin; releases specific hormone on demand in response to action potentials of that travel down axons of these same hypothalamic neurons

adenohypophysis

Anterior lobe of pituitary; composed of glandular tissue that arises from outpocketing of oral mucosa; manufactures and releases GH, TSH, ACTH, FSH, LH, PRL; releases specific hormone after receiving appropriate distinct chemical stimulus from hypothalamus

hypothalamic-hypophyseal tract

Nerve bundle that runs through infundibulum and maintains neural connection between posterior pituitary and hypothalamus from which it derives; arises from neurons in paraventricular and supraoptic nuclei of hypothalamus

supraoptic nucleus

One of two hypothalamic nuclei that contribute to hypothalamic-hypophyseal tract; neurosecretory cells that synthesize mainly ADH and transport it along axons to posterior pituitary, where it is released into capillaries for distribution throughout body

paraventricular nucleus

One of two hypothalamic nuclei that contribute to hypothalamic-hypophyseal tract; neurosecretory cells that synthesize mainly oxytocin and transport it along axons to posterior pituitary, where it is released into capillaries for distribution throughout body

neurohormone

Hormones secreted by neurons; examples include those secreted by posterior pituitary

hypophyseal portal system

Collective term for primary capillary plexus and hypophyseal portal vein of infundibulum and secondary capillary plexus of anterior lobe of pituitary; conduit for releasing and inhibiting hormones secreted by ventral hypothalamus that travel to anterior pituitary and regulate secretion of its hormones

pro-opiomelanocortin (POMC)

Prohormone produced by corticotropic cells of anterior pituitary; large precurser molecule that is split into corticotropin, also known as ACTH, and other molecules

tropic hormone

Hormone that regulates secretory action of other endocrine glands; examples include four of six anterior pituitary hormones - TSH, ACTH, FSH, and LH

melanocyte stimulating hormone (MSH)

Hormone derived from POMC in anterior pituitary; elevated blood levels occur with Addison's disease, in which adrenal cortex produces inadequate amounts of its steroid hormones, or with anterior pituitary gland tumors; causes bronzing of skin in these disease states; normal function in human unclear

growth hormone (GH)

Somatotropin protein produced by anterior pituitary; direct actions on metabolism; mobilizes fat, increases blood levels of fatty acids, and encourages their use for fuel; decreases glucose uptake and encourages glycogen breakdown; elevates blood glucose with overall glucose sparing effect; increases amino acid uptake into cells and incorporation into proteins; indirect actions on growth via IGFs; secretion controlled by releasing and inhibiting hormones from hypothalamus and negative feedback related to blood levels of relevant hormones; release stimulated by hypoglycemia, elevated blood levels of amino acids, low blood levels of fatty acids, exercise, and other stressors; daily cycle of release with highest levels during evening sleep

insulin-like growth factors (IGF)

Family of proteins that mediate growth-promoting effects of GH; those produced in liver act as hormones, while those produced in tissues such as skeletal muscle and bone act as paracrines; stimulate uptake of nutrients from blood and incorporation into proteins and DNA, allowing growth by cell division; stimulate formation of collagen and deposition of bone matrix; act on most body cells, but major targets are epiphyseal plates leading to long bone growth, and skeletal muscles leading to increased muscle mass

thyroid stimulating hormone (TSH)

Thyrotropin; glycoprotein tropic hormone produced in thyrotropic cells of anterior pituitary; affects target cells via cyclic AMP second messenger; stimulates normal development and secretory activity of thyroid gland; secretion controlled by releasing and inhibiting hormones from hypothalamus and negative feedback related blood levels of relevant hormones; daily cycle of release with lower levels during day, pleak just before sleep, and remaining high during night

adrenocorticotropic hormone (ACTH)

Corticotropin; peptide hormone split from POMC prohormone in corticotropic cells of anterior pituitary; affects target cells via cyclic AMP second messenger; stimulates adrenal cortex to release glucocorticoids and androgens, and to lesser extent mineralocorticoids; secretion controlled by releasing and inhibiting hormones from hypothalamus and negative feedback related to blood levels of relevant hormones; release stimulated by fever, hypoglycemia, and stressors of all types; daily cycle of release with levels peaking in morning shortly before waking

follicle stimulating hormone (FSH)

One of two gonadotropins present after puberty; glycoprotein hormone produced in gonadotropic cells of anterior pituitary; affects target cells via cyclic AMP second messenger; acts on ovaries in females to stimulate follicle maturation and estrogen production; acts on testes in males to stimulate sperm production; secretion controlled by releasing and inhibiting hormones from hypothalamus and negative feedback related to blood levels of estrogen and testosterone; during reproductive years in females, surge released midway in ovarian cycle approximately day 14

luteinizing hormone (LH)

One of two gonadotropins present after puberty; glycoprotein hormone produced in gonadotropic cells of anterior pituitary; affects target cells via cyclic AMP second messenger; acts on ovaries in females to trigger ovulation and stimulates estrogen and progesterone production; acts on testes in males to stimulate testosterone production; secretion controlled by releasing and inhibiting hormones from hypothalamus and negative feedback related to blood levels of estrogen, progesterone, and testosterone; during reproductive years in females, surge released midway in ovarian cycle approximately day 14

prolactin (PRL)

Protein hormone produced in anterior pituitary; affects target cells via cyclic AMP second messenger; acts on breast secretory tissue to promote lactation; unlike other anterior pituitary hormones, released controlled primarily by inhibitory hormone, dopamine, with releasing factors not well understood; in non-pregnant females, levels rise and fall in rhythm with estrogen blood levels, which stimulate stimulates release; in pregnant females, levels rise dramatically toward end of pregnancy and milk production becomes possible; infant suckling stimulates releasing factors in mother, encouraging continued milk production; role in males not well understood

oxytocin

Peptide produced mostly in neurons of paraventricular nucleus in hypothalamus; affects target cells via PIP₂-Ca²⁺ second messenger; acts on uterus to stimulate contractions and initiate labor; acts on breast to initiate milk ejection; secretion controlled by positive feedback mechanisms, rare form of feedback control in body; levels peak with increased stretching of uterus leading up to labor, and each time an infant suckles breast; also neurotransmitter in brain involved with sexual and affectionate behavior, promoting nurturing, couple bonding, and trust

thyroxine (T4)

Major hormone secreted by thyroid follicles; consists of two linked tyrosine amino acids with four bound iodine atoms; less active in peripheral tissues; secretion, transport, target cell effect, and regulation similar to its more potent counterpart; secretion controlled by levels of TSH

triiodothyronine (T3)

Hormone formed mostly at target cells by enzymes that remove one iodine atom from thyroxine; consists of two linked tyrosine amino acids with three bound iodine atoms; ten times more active in peripheral tissue than predominant form of thyroid hormone secreted by thryoid gland; affects target cells via binding to nuclear receptor and initiating transcription of mRNA for protein synthesis; affects almost all body cells; increases basal metabolic rate and body heat production via effect on glucose oxidation; critical for regulating normal skeletal and nervous system development and maturation; enables reproductive capabilities; maintains blood pressure by increasing number of adrenergic receptors in blood vessels

thyroxine-binding globulin (TBG)

Transport protein produced by liver that circulates in blood; immediately binds most T₃ and T₄ released by thyroid gland for transport in blood, since they are not water soluble; releases T₃ and T₄ to target cells

adrenal medulla

Inner portion of adrenal gland that is knot of nervous tissue, part of sympathetic nervous system; composed of medullary chromaffin cells, crowded around blood-filled capillaries and sinusoids; chromaffin cells are modified postganglionic sympathetic neurons that synthesize catecholamines; stimulated by preganglionic fibers during sympathetic response to short-term stressor

adrenal cortex

Outer portion which constitutes bulk of adrenal gland; glandular tissue derived from embryonic mesoderm; synthesizes over two dozen steroid hormones, corticosteroids, from cholesterol; large lipid laden cells arranged in three layers; most superficial layer, zona golmerulosa, clustered cells produces mineralocorticoids for water and electrolyte balance; middle layer, zona fasciculata, cells arranged in linear cords produce mainly glucocorticoids for metabolic regulation; innermost layer, zona reticularis, netlike arrangement of cells that produce mainly gonadocorticoids; stimulated by prolonged stressors

mineralocorticoids

Steroid hormones produced in zona glomerulosa of adrenal cortex; aldosterone is most potent version and accounts for more than 95% produced; regulate electrolyte concentration of extracellular fluids; strongest stimuli for release are renin-angiotensin-aldosterone mechanism, and plasma concentrations of potassium; contribute to countering stressors by kidney retention of salt and water, thus raising blood volume and pressure

glucocorticoids

Steroid hormones produced mostly in zona fasciulata of adrenal cortex; mostly cortisol; promote gluconeogenesis and hyperglycemia; mobilize fats for energy metabolism; stimulate protein catabolism; stimulus for release is ACTH from anterior pituitary; contribute to countering stressors by glucose sparing to help fuel brain

gonadocorticoids

Steroid hormones produced mostly in zona reticularis of adrenal cortex; mostly weak androgens such as androstenedione and dehydroepiandrosterone DHEA; most converted in tissue cells to more potent male hormones, such as testosterone, and some are converted to estrogen; amount produced by adrenal cortex insignificant compared to that made by gonads during late puberty and adulthood; exact role still in question; in females, contribute to libido and is primary source of estrogen after menopause

cortisol

Primary glucocorticoid secreted by adrenal cortex; affects target cells via binding to nuclear receptor and initiating transcription of mRNA for protein synthesis; affects most body cells and stimulates lipolysis and fat mobilization, gluconeogenesis, and catabolism of proteins; under normal circumstances, helps body adapt to intermittent food intake, with secretory bursts driven by patterns of eating and activity; secretion controlled by ACTH from anterior pituitary and negative feedback; prolonged or severe stress overrides negative feedback and blood levels rise dramatically, resulting in depressed cartilage and bone formation, inhibition of inflammation by decreasing release of inflammatory chemicals, depressed immune system, and disruption of normal cardiovascular, neural, and gastrointestinal function

catecholamine

Biogenic amines synthesized by medullary chromaffin cells by medullary chromaffin cells of adrenal medulla; synthesized via molecular sequence from tyrosine to dopamine to norepinephrine to epinephrine; 80% of hormone stored and released is epinephrine, 20% norepinephrine; epinephrine is more potent stimulator of metabolic activities, bronchial dilation, and increased blood flow to skeletal muscle and heart; norepinephrine has greater influence on peripheral vasoconstriction and blood pressure; reinforce and prolong fight-or-flight sympathetic response to short-term stressor

estrogen

Steroid hormones produced in much greater quantities by ovary than adrenal cortex; secreted from developing follicles and corpus luteum; secretion controlled by FSH and LH from anterior pituitary and negative feedback, along with positive feedback during ovulation, over 28 day cycle; affects target cells via binding to nuclear receptor and initiating transcription of mRNA for protein synthesis; responsible for appearance of secondary sex characteristics of females at puberty, maturation of reproductive organs and breasts, oogenesis, proliferative phase of uterine cycle, watery cervical mucus, activity of fimbriae, and portion of female libido; large quantities produced by placenta during pregnancy

progesterone

Steroid hormone produced in much greater quantities by ovary than adrenal cortex; secreted by corpus luteum; secretion controlled by LH from anterior pituitary and negative feedback over last 14 days of ovarian cycle; affects target cells via binding to nuclear receptor and initiating transcription of mRNA for protein synthesis; responsible for cooperating in breast growth, secretory phase of uterine cycle, viscous cervical mucus, enhanced beating of cilia in uterine tube; large quantities produced by placenta during pregnancy for main role in quieting myometrium to prevent contraction

testosterone

Steroid hormone produced in much greater quantities by testes than adrenal cortex; secreted by interstitial endocrine cells; secretion controlled by LH from anterior pituitary and negative feedback; affects target cells via binding to nuclear receptor and initiating transcription of mRNA for protein synthesis; responsible for formation of male ducts, glands, and external genitalia during development, and descent of testes; responsible for appearance of secondary sex characteristics of males at puberty, maturation of reproductive organs, and enabling spermatogenesis; responsible for libido and promotes aggressiveness

testes

Male gonads; produce sperm and sex hormones; Pair of plum sized organs located in scrotum; approximately 1.5 in. long by 1 in. wide; covered externally by tunica albuginea that extends internally to divide it into 250 lobules; each lobule contains seminiferous tubules surrounded by smooth muscle-like myeloid cells that contract rhythmically to move sperm and fluid through tubules; contain interstitial endocrine cells that produce androgens; panpiniform venous plexus keeps cooled to homeostatic optimum

seminiferous tubules

One to four tightly coiled structures within each lobule of testes; sperm factories of thick stratified epithelium surrounding central fluid containing lumen; epithelium consists of spheroid spermatogenic cells embedded in substantially larger columnar cells, sustentocytes, with supporting roles in sperm function

penis

Copulatory organ portion of male external genitalia; designed to deliver sperm into female reproductive tract; consists of root, shaft, and enlarged glans at tip covered with cuff of skin, prepuce; internally contains spongy urethra and three bodies of erectile tissue; surrounding longitudinal and circular arrangement of collagen fibers prevents kinking or buckling when erect during intercourse

corpora cavernosa

Paired dorsal erectile bodies that make up most of penis; bound by fibrous tunica albuginea; internal spongy network of connective tissue and smooth muscle riddled with vascular spaces that fill with blood during sexual arousal, causing penis to enlarge and become rigid

epididymis

Par of male accessory duct system; cup shaped structure with efferent ductule containing head that caps superior aspect of testis; mostly highly coiled ducts, approximately 20 ft.; some pseudostratified epithelial cells of duct mucosa exhibit long, nonmotile microvilli, stereocilia, that absorb excess testicular fluid and pass nutrients to may sperm stored temporarily in lumen; over about 20 day period immature, nearly nonmotile sperm moved slowly through fluid that contains several kinds of antimicrobial proteins, and gain ability to swim; site from which sperm are ejaculated; stores sperm for several months, and has epithelial cells that phagocytize sperm if not used

ductus deferens

Part of male accessory duct system; 18 in. duct running upward as part of spermatic cord from epididymis through inguinal canal into pelvic cavity; lined with pseudostratified epithelia; easily palpated as it passes anterior to pubic bone, it then loops medially over ureter and descends along posterior bladder wall; terminus expands to form ampulla which joins duct of seminal gland to form ejaculatory duct; muscular layer is extremely thick making duct feel like hard wire; during ejaculation smooth muscle creates strong peristaltic waves that rapidly squeeze sperm forward along tract and into urethra

seminal vesicles

One of male accessory glands; large hollow glands that is pouched, coiled, and folded back on itself, with shape and length of a little finger and lies on posterior bladder surface; fibrous capsule encloses thick layer of smooth muscle that contracts during ejaculation to empty gland; mucosa is secretory pseudostratified columnar epithelium; stored within crypts is yellowish viscous alkaline fluid containing fructose, citric acid, coagulating enzyme, prostaglandins, and other substances that enhance sperm motility or fertilizing ability, and account for 70% of semen volume; joins ductus deferens to form ejaculatory duct

prostate

One of male accessory glands; single doughnut-shaped, peach-pit sized gland that encircles urethra just inferior to bladder; enclosed by thick connective tissue capsule and made up of 20 to 30 compound tubuloalveolar glands embedded in smooth muscle and dense connective tissue; during ejaculation, smooth muscle contracts squeezing secretions into urethra via several ducts; fluid has role in activating sperm and is roughly one-third of semen volume; secretion is milky, slightly acidic and contains citrate as nutrient source, several enzymes including fibrinolysin, hyaluronidase, and acid phosphatase, and prostate specific antigen

bulbourethral gland

One of male accessory glands; pea-sized and located inferior to prostate in urogenital diaphragm; produces thick, clear mucus, some of which drains into spongy urethra and lubricates glans penis during sexual arousal; mucus produced neutralizes traces of acidic urine and lubricates urethra just prior to ejaculation; contents released in response to parasympathetic stimulation

semen

Milky white, somewhat sticky mixture of 10% sperm and balance of testicular fluid and accessory gland secretions; provides cellular transport medium and nutrients and contains chemicals that protect, activate, and facilitate movement of millions of sperm ejaculated in 2-5 ml volume; prostaglandin component decreases viscosity of cervical mucus and stimulates reverse peristalsis in uterus, facilitating sperm movement through female reproductive tract; relaxin and certain enzyme components enhance sperm motility; ATP component provides energy; certain components suppress immune response in female reproductive tract; antibiotic component destroys some bacteria; clotting factor component causes sperm to stick to walls of vagina and prevent initially immobile sperm from leaking out; fibrinolysin component liquefies sticky mass and sperm swim out into female duct system; 7.2-7.8 pH neutralizes acidity of male urethra and female reproductive tract and enhances sperm motility

erection

First of two major phases of male sexual response; enlargement and stiffening of penis, resulting from engorgement; sexual excitement triggers parasympathetic reflex that promotes local release of NO that relaxes smooth muscle in penile blood vessel walls, dilating arterioles, and erectile bodies fill with blood; rare example of parasympathetic control of arterioles, and mediated by pudendal nerves; expansion of corpora cavernosa of penis compresses their drainage veins, retarding blood outflow and maintaining engorgement; stimulated by erotic touch, sight, sound, smell, or even emotional or higher mental activity which may also inhibit; equivalent to female engorgement of clitoris

ejaculation

Second of two major phases of male sexual response; propulsion of semen from male duct system; impulses provoking erection reach critical level, initiating spinal reflex and massive discharge of nerve impulses over sympathetic nerves, largely at L₁ and L₂ levels, serving genitals; bladder sphincter muscle constrict, preventing expulsion of urine or reflux of semen into bladder; reproductive ducts and accessory glands contract, emptying contents into urethra; semen in urethra triggers spinal reflex through somatic motor neurons triggering bulbospongiosus muscles of penis to undergo series of rapid contractions propelling semen from urethra at 11 mi/h; rhythmic contractions accompanied by intense pleasure and many systemic changes such as generalized muscle contraction, rapid heartbeat, and elevated blood pressure; quickly followed by resolution, period of muscular and psychological relaxation, and then latent period ranging from minutes to hours, increasing with age

sperm

Male gamete; haploid spermatozoon with unique combination of genetic characteristics; head almost entirely flattened nucleus with compacted DNA; helmet-like acrosome adhered to top of nucleus and contains hydrolytic enzymes that enable penetration of egg; midpiece contains mitochondria that provide ATP for whiplike tail movement; long tail is flagellum produced by one centriole, actually basal body, near nucleus; 64-72 day formation occurs continuously in seminiferous tubules begining in puberty under hormonal influence, and production typically remains stable until very advanced age

blood-testis barrier

Created by sustentocytes bound to each other laterally by tight junctions in seminiferous tubules; prevents membranes antigen of differentiating sperm in adlumenal compartment from escaping through basal lamina into bloodstream and activating immune system; important because no sperm are formed until puberty, so they are absent when immune system is programmed to recognize self tissues early in life

ovaries

Female gonads; produce female gametes and sex hormones; shaped like almonds and twice as large; flank uterus on each side and held in place by ovarian and suspensory ligaments and mesovarium; surrounded externally by fibrous tunica albuginea; highly vascular connective tissue of cortex contains many follicles at different stages of maturation and typically one corpus luteum per cycle; medulla contains largest blood vessels and nerves; with age surface has increasing numbers of corpus albicans scars revealing where many oocytes were released

ovarian follicles

Tiny saclike structures embedded in ovarian cortex; consists of oocyte encased by one or more layers of very different cells, called follicle cells if one layer, and granulosa cells if more than one; hundreds of thousands visible on ovary cortex at varying stages of development, ranging from primordial to most mature with large fluid filled antrum that bulges from surface of ovary; typically one per month ejects oocyte during ovulation and transforms into corpus luteum; grow, mature, and secrete sex hormones in response to FSH and LH; granulosa cells of late secondary and vesicular versions release estrogen during first half of ovarian cycle

corpus luteum

Glandular structure in ovary created from ruptured follicle after ovulation in response to LH surge; enlarged granulosa cells and internal thecal cells that now secrete progesterone and some estrogen during second half of ovarian cycle; degenerates when LH levels fall near end of cycle without fertilization, and becomes corpus albicans

uterine tubes

Initial part of female duct system; receive ovulated oocyte and where fertilization generally occurs; 4 in. long ducts extend medially from ovary to empty into superolateral regions on each side of uterus; supported by mesosalpinx mesentery; around time of ovulation, bend to drape over ovary; duct wall is sheets of smooth muscle and thick highly folded mucosa with ciliated cells; oocyte is carried along internal hair width diameter toward uterus by peristalsis and beating cilia; nonciliated cells have microvilli and produce secretions that keep oocyte, and sperm if present, moist and nourished

fimbriae

Ciliated, fingerlike projections on funnel-shaped open end of oviduct, infundibulum; at time of ovulation, stiffen and sweep ovarian surface with beating cilia creating currents in peritoneal fluid that draw oocyte into uterine tube

uterus

Hollow, thick walled, muscular organ that receives, retains, and nourishes fertilized ovum; where embryo/fetus develops; located in pelvis anterior to rectum and superior to bladder, and inclined forward; size and shape of inverted pear in women that have never been pregnant, and larger following pregnancy; wall composed of perimetrium, myometrium, and endometrium; consists of body, fundus, and cervix; supported by mesometrium, lateral cervical ligaments, utersacral ligaments, and round ligaments; during pregnancy enlarges remarkably, reaching level of xiphoid process and occupying most of abdominal cavity

cervix

Narrow neck, or outlet, of uterus that projects into vagina inferiorly; canal communicates with vagina, and mucosa secretes mucus that fills it, presumably to block spread of bacteria from vagina to uterus; thick, sticky mucus also blocks sperm entry except at midcycle when rising estrogen levels cause it to becomes less viscous, thinning and forming channels that allow sperm to pass; rising progesterone levels during second half of ovarian cycle, and during pregnancy, stimulates thick cervical mucus plug to keep uterus private; softening, thinning, and dilation of this portion of uterus occur during first stage of labor

myometrium

Bulky middle layer of uterus composed of interlacing bundles of smooth muscle; contracts rhythmically during childbirth to expel baby; during last few weeks of pregnancy when estrogen levels peak, cells form abundant oxytocin receptors, gap junctions form between smooth muscle cells, and this uterine layer becomes increasingly irritable and likely to contract

endometrium

Mucosal lining of uterine cavity, composed of simple columnar epithelium over thick lamina propria; site where young embryo implants and resides for development; superficial stratum functionalis layer undergoes cyclic changes in response to blood levels of ovarian hormones and is shed during menstruation approximately every 28 days; spiral arteries of stratum functionalis repeatedly degenerate and regenerate, with spasms causing functionalis to shed during menstruation; thinner stratum basalis layer forms new functionalis after menstruation; contains numerous uterine glands that change cyclically, whose purpose is to secrete nutrients into uterine cavity to sustain potential embryo until implantation

vagina

Thin-walled tube, 3-4 in. long that lies between bladder and rectum and extends from cervix to body exterior; passageway for delivery of infant and menstrual flow; receives penis and semen during sexual intercourse and is female organ of copulation; stretches considerably during copulation and intercourse; walls consist of deep fibroelastic adventitia, middle smooth muscle muscularis, and superficial mucosa with transverse ridges; mucosa is stratified squamous epithelium adapted to stand up to friction; dendritic antigen presenting cells line mucosa; epithelial cells release large amounts of glycogen which resident bacteria metabolize to lactic acid; acidic pH in adults prevents infection, but alkaline pH in adolescents predisposes them to sexually transmitted infections; mucosa near distal orifice forms incomplete partition, hymen;

greater vestibular glands

Part of female external genitalia; pea-sized glands flanking vaginal opening; homologous to bulbourethral glands in males; release mucus into vestibule and help keep it moist and lubricated, facilitating intercourse

clitoris

Small, protruding structure composed largely of erectile tissue, just anterior to vestibule; homologous to male penis; exposed portion is glans, which is hooded by skin fold, prepuce, formed by junction of labia minora folds; richly innervated by nerve endings sensitive to touch; becomes swollen with blood and erect during tactile stimulation, contributing to female sexual arousal

secondary oocyte

Haploid cell with unique combination of genetic characteristics; cell produced by dominant ovarian follicle each month; larger of two cells produced by meiotic division, contains most cytoplasm and organelles; arrested in metaphase II, which is completed only if sperm penetrates it and it becomes ovum, functional female gamete; approximately 500 released over reproductive lifetime from age 11-51

ovarian cycle

Monthly series of events, occurring in two consecutive phases, associated with maturation of one egg; follicular phase, days 1-14, dominant follicle is selected and begins to secrete large amounts of estrogen, culminating in ovulation when secondary oocyte released into peritoneal cavity; luteal phase, days 14-28, ruptured follicle becomes corpus luteum producing estrogen and progesterone for remainder of cycle, then degenerates if fertilization does not occur; 10-15% of women have typical 28 day cycle, but those ranging from 21-40 days are fairly common, with length of follicular phase being one that varies; regulated by waxing and waning of anterior pituitary hormones and ovarian hormones and negative and positive feedback interaction

uterine cycle

Series of changes that endometrium goes through each month as it responds to waxing and waning of ovarian hormones in blood; endometrial changes are coordinated with phases of ovarian cycle; during menstrual phase, days 1-5, functional layer sloughs off in menses; proliferative phase, days 6-14, rising estrogen levels stimulate regeneration of functional layer, making uterus receptive to implantation about one week after ovulation; secretory phase, days 15-28, uterine glands secrete nutrients and endometrial vascularity increases further; falling levels of ovarian hormones during last few days of cycle cause spiral arteries to become spastic and cut off blood supply of functional layer, triggering menstruation and beginning of new cycle

sexually transmitted infections

Infectious diseases spread through sexual contact; U.S. has highest rates of infection among developed countries; over 12 million people, a quarter of them adolescents, acquire each year; preventable with condoms; single most important cause of reproductive disorders; some have systemic effects and some implicated in cancer; examples include gonorrhea, syphilis, chlamydia, trichomoniasis, genital warts, genital herpes, and AIDS

puberty

Interval when reproductive organs grow to adult size and become functional; occurs in response to rising levels of gonadal hormones, testosterone in males and estrogen in females; events occur in same sequence in all individuals, but age of occurrence varies widely; in males, enlargement of testes and scrotum occurs between ages of 8-14, with penis growth over next two years, and sexual maturation evidenced by presence of mature sperm in semen; unexpected erections and nocturnal emissions occur as hormones surge and hormonal control axis struggles to achieve normal balance; in females, breasts bud between ages of 8-14 and menarche occurs about two years later; dependable ovulation and fertility await maturation of hormonal controls, which take another two years; accompanied by development of secondary sex characteristics; epiphyseal plate closure and termination of skeletal growth in height occurs in response to rising estrogen levels during late stages in both boys and girls

menopause

Period of life when, prompted by hormonal changes, ovulation and menstruation cease; preceded by period of declining control evidenced by anovulation, multiple ovulations, and menses that becomes erratic and increasingly shorter; begins when whole year has passed since menstruation; typically occurs between 46-54; ovaries stop functioning as endocrine organ and estrogen levels drop, resulting in reproductive and breast atrophy, dry vagina, and increased prevalence of vaginal infections; decreased estrogen may also cause irritability and depression, intense vasodilation of skin blood vessels and uncomfortable hot flashes, gradually thinning skin, loss of bone mass, rising cholesterol, and falling HDL; hormone replacement therapy in smallest dose for shortest period may be beneficial

gestation period

Timeframe when conceptus development occurs; approximately 280 days; extends from beginning of last menstrual period until birth; at moment of fertilization, mother is two weeks pregnant

conceptus

Pregnant woman's developing offspring; includes all stages of development from embryo through fetus

embryo

Conceptus developmental stage from fertilization through week 8; characteristics of conceptus at end of stage include: all major brain regions present and first brain waves appear in brain stem, liver forms blood cells, limbs present, ossification begins, spontaneous muscle contractions, cardiovascular system fully functional with heart pumping since week 4, all body systems present in rudimentary form, 0.9 in. and .06 oz.

fetus

Conceptus developmental stage from week 9 through birth; time of rapid growth of organs established during previous 8 weeks; weeks 9-12, bone marrow assists liver with blood cell formation and sex readily visible from genitals; weeks 13-16, blinking of eyes and sucking motions of lips, body growth begins to outpace that of head, and meconium is collecting; weeks 17-20, vernix caseosa covers body, skin lanugo, body flexes anteriorly due to space restrictions, and quickening; weeks 21-30, substantial increase in weight, may survive if premature but temperature regulation and lung surfactant still inadequate, myelination of spinal cord begins, limb bones begin ossifying, nails present, tooth enamel forming, and testes reach scrotum; weeks 30-40, term, fat laid down in hypodermis, crown-rump length 14 in., and weight 7 lb.

fertilization

Sperm's chromosomes combine with those of ovum following fusion of male and female pronuclei to form zygote; typically occurs in uterine tube, midway through ovarian cycle, during 12-24 hour window of secondary oocyte viability following appropriately timed intercourse; marks beginning of embryonic development