Lecture Exam: Reproductive System Flashcards
biparental
offspring receive genes from two parents so not identical to each other each produces games (sex cells) combining in a zygote (fertilized egg).
necessary for gametes
Gamete motility is necessary to achieve contact (small motile) and nutrients for developing embryo (large and heavy)
male reproductive system serves to
Males have a copulatory organ (penis) for introducing their gametes into the female reproductive tract
female reproductive system produces
Female reproductive system produces eggs, receives sperm, provides for gametes’ union, harbors fetus, and nourishes offspring. Sheleterd internal environment for development and nutrition of egg
Females have a copulatory organ (vagina) for receiving the sperm
primary sex organs
gonads produce gametes
secondary sex organs
endocrine help w/ reproduction
where are genitalia located?
im male Most are external genitalia except for accessory glands.
female most is internal in perineum located in pelvic cavity
secondary sex characteristics for both sexes
features that distinguish the sexes and influence mate attraction ex.
Develop at puberty
Both sexes- Pubic and axillary hair and their associated scent glands, and the pitch of the voice
secondary sex characteristic for male
Facial hair, coarse and visible hair on the torso and limbs, relatively muscular physique. Secondary sex organs: ducts, glands, and penis
secondary sex characteristic for female
Distribution of body fat, breast enlargement, and relatively hairless appearance of the skin secondary sex organs: uterine tubes, uterus, and vagina
sexually differentiation occurs and how does this happen
fetus is sexually undifferentiated at first until 5-6 weeks
Gonads begin to develop as gonadal ridges w/ two ducts: mesonephric duct (serves mesonephros) developing into reproductive tract in males not females, and paramesonephric duct degenerates in males reproductive tract in females. Estrogen levels always high during pregnancy, development of female results from absence of androgen and mulleran-inhibitting factor .
what gene is found only in males? what does it do?
SRY gene (sex-determining region of Y chromosome)
SRY codes for a protein, testis-determining factor (TDF), that initiates development of testes
Testes begin to secrete testosterone at 8 to 9 weeks
Stimulates mesonephric ducts to develop into male tracts
At same time, the testes secrete müllerian-inhibiting factor causing degeneration of the paramesonephric ducts
development of external genitalia
homologous development among both sexes from same embryonic structures. genital tubercle becomes the (head and glands) penis and clitoris glans, male and female respectively; urogenital folds enclose urethra, as well as labia minora; urogenital folds become the scrotum and labia majora, fully distinguishable by 12 weeks.
descent of the testis
Both sexes gonads develop high in the gonadal cavity near kidneys migrate into pelvic cavity (ovaries and scrotum).
steps of descent of organs: Gubernaculum,
connective tissue cord anchors gonads to floor of abdominopelvic cavity passing between the male internal and external abdominal oblique muscles into scrotal swelling
steps of descent of organs:peritoneum
Peritoneum develops fold extending into scrotum as vaginal process independent of gubernaculum.
steps of descent of organs: inguinal canal
Inguinal canal- gubernaculum and vaginal process create path of low resistance through groin, anterior to pubic symphysis, most common site for herniation in men.
steps of descent of organs: testes
Testes descend beginning week 6-8. Superior part of embryonic gonad degenerates w/ inferior part migrating downward guided by gubernaculum. Seventh month testes pass through inguinal canal into scrotum accompanied by testicular arteries, veins, nerves, lymph vessels, spermatic duct, and internal oblique muscle.
steps of descent of organs:vaginal proces
Vaginal process separated from peritoneal cavity becoming sac
steps of descent of organs: tunica vaginalis
Tunica vaginalis- enfolding anterior and lateral sides of testis protecting from abrasion against scrotum w/ movements of body
steps of descent of organs: cryptorchidism
Cryptorchidism- 3% of boys undescended testes that descend w/in first year of infancy, if not corrected w/ testosterone or surgery; uncorrected leads to sterility and testicular cancer
steps of descent of organs: ovaries
Ovaries descend to lesser extent, gubernaculum (becoming ligaments for support) extends from inferior pole of ovary to labioscrotal fold lodge inferior to brim
Reproductive system remains dormant
for several years after birth 10-12 years in boys, 8-10 in females, surge of pituitary gonadotropins awakens puberty
Testes secrete testosterone
in first trimester of fetal development as high as midpuberty then become dormant during infancy and childhood. As hypothalamus matures in late childhood begins to secrete (GnRH) to anterior pituitary to release FSH and LH need both for sperm production, which act on gonads rest regulated by these three throughout hormone.
LH effect on male reproduction
- interstitial cell-stimulating hormone stimulating endocrine cells to secrete androgens, testosterone. Promoting sperm production
FSH-effect on male reproduction
stimulates nurse cells of testes to secrete androgen-binding protein binding and accumulating testosterone in seminiferous tubules and epididymis, spermatogenesis
Adolescence in men
period from onset of gonadotropin secretion and reproductive development to when a person attains full adult height
Puberty in men
first few years of adolescence, until the first menstrual period in girls or the first ejaculation of viable sperm in boys. Growth of sex organs: testes, scrotum, ducts and glands. Sperm production by testosterone as well as limb bones elongate rapidly growing taller w/ more muscle mass. Larynx enlarges deepening voice and making thyroid cartilage more prominent, higher RBC count increasing basal metabolic rate and appetite. Testosterone stimulates brain awakening libido converting to estrogen (causing wet dreams). Dehydrin testosterone-develops pubic hair, axillary hair, facial hair, thicker darker skin more sebum, scent glands.
Adulthood in men
testosterone sustains male reproductive tract, sperm production, and helps maintain libido. Inhibin from nurse cells suppresses FSH decreasing sperm production w/out reducing LH and testosterone secretion.
Aging and Sexual Function-
Due to decline in activity and edrogencells, Testosterone secretion declines with age
Peak secretion at 7 mg/day at age 20; declines to one-fifth of that by age 80
Decline in number and activity of interstitial endocrine cells
Male climacteric (andropause)
may occur
A period of declining reproductive function that may be first seen in early 50s
Although sperm counts decline, men can still father children throughout old age
age related drop in testosterone inhibin triggers rise in FSH and LH drive can experience mood changes, hot flashes, and allusions of suffocation
can lead to impotence or erectile dysfunction 20% of men in 60s and 50% in 80s, inability to produce or maintain erection
Spermatogenesis—
process of sperm production in seminiferous tubules
spermatogenesis Involves three principal events
Division and remodeling of large germ cells into small, mobile sperm cells with flagella
Reduction of chromosome number by one-half
Shuffling of genes so each chromosome contains new gene combinations that did not exist in parent
Ensures genetic variation in the offspring
Meiosis
recombines genes and reduces chromosome number, while producing four daughter cells, gametes that are haploid cells that will become sperm and combine w/ egg to produce diploid fertilized egg
Half genetic material reduction division, two cell division one replication of DNA w/ each having four stages.
spermatogenesis: primordial germ cell
Begin as primordial germ cells form in yolk sac, crawl into embryo itself colonizing gonadal ridges becoming stem cells spermatogonia remaining dormant throughout childhood, lying along periphery of seminiferous tubules near basement membrane outside blood testis barrier
spermatogenesis: spermatogonia
Puberty testosterone secretion rises. Spermatogonia divide by mitosis, one daughter cell remains near tubule wall as type A spermatogonium lifetime supply of stem cells, other daughter cell is type B spermatogonia migrating away from wall.
spermatogenesis: primary blood barrier
Type B spermatogonia enlarges becoming primary spermatocyte, protected by nurse cells w/ tight junction dismantled allowing movement through to protected area.
spermatogenesis: primary spermatocyte
Primary spermatocyte undergoes meiosis I, giving rise to two equal size haploid and genetically unique secondary spermatocytes
spermatogenesis: secondary spermatocyte
Secondary spermatocyte undergoes meiosis II dividing into two spermatids four for each spermatogonium then undergoes spermatogenesis differentiating into single spermatozoon sprouting tail and discarding cytoplasm towa.
mature spermatazoon
Head-pear shaped containing nucleus w/ haploid DNA, acrosome (lysosome for egg) and flagella basal body. Tail- three different regions midpiece- contains mitochondria ATP for flagella movement, principa- axoneme supporting fibers most of tail. Endpiece- tip of flagella.
semen
(seminal fluid)—fluid expelled during orgasm.
2 to 5 mL of fluid expelled during ejaculatiom
60% seminal vesicle fluid, 30% prostatic fluid, and 10% sperm and spermatic duct secretions
Normal sperm count 50 to 120 million/mL
Lower than 20 to 25 million/mL: infertility
prostate produces
thin, milky white fluid
Contains calcium, citrate, and phosphate ions
Clotting enzyme
Protein-hydrolyzing enzyme called serine protease (prostate-specific antigen)
seminal vesicle
Seminal vesicles contribute viscous yellowish fluid
Contains fructose and other carbohydrates, citrate, prostaglandins, and protein called proseminogelin. Stickines sof semen promotes fertilization, clotting enzyme activates prosemenogelin to semenogelin entangling sperm sticking to walls of inner vagina and cervix ensuring that semen doesn’t drain out, and can promote uptake of sperm-laden clots of semen into uterus. 20-30 minutes after ejaculation, serine protease of fluid breaks down semenogelin liquefying it.
sperm motility needs?
Sperm motility required to have elevated pH and energy source (sugars from seminal vesicles). Spermatic fluid buffers vagina and seminal acidity raising pH significantly activating sperm. Activated sperm crawl up thin mucosa of vagina and uterus. Prostaglandins of semen thin mucus and cervical canal of female for easier migration into uterus, stimulate peristaltic waves in uterus and uterine tubes helping to spread semen through female reproductive tract.
circulation to penis during arousal
internal iliac artery gives rise to internal pudendal (penile artery), root of penis, dividing into two dorsal branches under skin dorsal surface- supplies most when flaccid innervating skin, fascia, and corpus spongiosum. Deep artery- travels through core of corpus cavernosum giving off helicine arteries penetrating trabeculae emptying into lacunae filling w/ blood becoming erect. Numerous anastomosis between deep and dorsal arteries allowing for full erection throughout.
Innervation to penis during arousal
Richly innervated by sensory and motor nerve fibers w/ glans and foreskin having abundance of tactile, pressure and temperature receptors. Lead by dorsal nerves to internal pudendal lead to sacral spinal cord autonomic somatic impulses from spine to penis induce sympathetic: erection based on thoughts and senses. Parasympathetic: direct stimulation of penis and perineal region
Divided intercourse
(aka coitus,coition,or copulation) into four recognizable phases- excitement plateau orgasm resolution
Excitement phase of intercourse in men
vasocongestion (swelling of genitals w/ blood), myotonia (muscle tension), increase in heart rate, blood pressure, and pulmonary ventilation. Bulbourethral glands secrete fluid during this phase. Initiated by erotic stimuli: sights, sounds, aromas, touch, dreams or thoughts w/ emotions inhibiting. Erection due to parasympathetic triggering of nitric oxide dilating arteries and filling lacunae w/ blood. Vasocongestion (50% larger) erection for entry into vagina.
Plateau: phase of intercourse in men
marked increase in respiratory, heart rate, and blood pressure continued increase vasocongestion and myotonia few minutes before orgasm.
Orgasm phase of intercourse in men
climax short but intense reaction marked by the discharge of semen lasting 3-15 seconds vitals increased. Heart rate increases to 180 beats/min, blood pressure rises, and breathy very elevation.
Ejaculaiton phase of intercourse in men
Ejaculaiton occurs in two stages: emission (sympathetic nervous system stimulates peristalsis propels sperm through ducts as glandular secretions are added) expulsion (semen in urethra activates somatic and sympathetic reflexes stimulating muscle contractions leading to expulsion. Contracts internal urethra sphincters so urine cannot pass during this time. Ejaculation and Orgasm are separate usually occur together but not always.
Resolution- body vitals return to normal sympathetic signals constrict internal pudendal artery reducing blood flow to penis becoming soft and flaccid, cardiovascular and respiratory return to normal w/ a refractory period 10 minutes to a few hours following intial impossible for male to maintain another erection.
Female reproductive system in comparison to the male system
The female reproductive system is more complex than the male system because it serves more purposes. Female system is more cyclic, and hormones are secreted in a more complex sequence
puberty begins what hormones involved and what do they do
at age 8 to 10 for most girls in United States
Triggered by rising levels of GnRH which stimulates anterior pituitary to secrete FSH and LH
FSH stimulates ovarian follicles and they begin to secrete estrogen, progesterone, inhibin, and a small amount of androgen
Estrogens are feminizing hormones with widespread effects on the body
Estradiol (most abundant), estriol, and estrone
three stages of puberty
Thelarche, pubarche, menarche,
thelarche
- onset of breast development, sign of onset of puberty, estrogen progesterone, and prolactin trigger the development of ducts and lobules completion of Governed by glucocorticoids growth hormone, adipose and fibrous tissue enlarge breast tissue
Pubarche-
appearance of pubic and axillary hair, sebaceous and axillary glands. androgens from ovaries and adrenal glands stimulate this as well as libido
Menarche-
first menstrual period requires 17% body fat, improved nutrition lowering onset, leptin stimulates gonadotropin secretion if both levels too low then menstrual cycle stops. If started only drops if below 22% body fat. Ovulating regularly year later.
Estradiol in puberty
changes of puberty: metaplasia of vaina, growth of ovaries and secondary sex organs, growth hormones leading to changes in height, widening of pelvis, fat deposition in feminine areas, thickens girls skin thinner softer and warmer than males.
Progesterone in puberty
- acts on uterus during second half of menstrual cycle preparing from possible pregnancy
Estrogen and progesterone- in puberty
suppress FSH and LH secretion by anterior pituitary through negative feedback, inhibin regulates FSH secretion.cyclic in specific sequence.
Climacteric and Menopause-
Females are born w/ 2 million eggs, climacteric when 1000 left Climacteric—midlife change in hormone secretion when 1000 left
Accompanied by menopause
climacteric
cessation of menstruation.
less responsive to gonadotropin secretes less estrogen and progesterone. Uterus, vagina and breastatrophy, intercouse uncomfrotable causing infections more easily, thinner skin, cholesterol rises, increase in cardiovascular disease, bone mass decline, shifting hormones and dilation causing hot flashes. Hormone replacement therapy relieve symptoms (low doses of estrogen and progesterone)
Menopause—
cessation of menstrual cycles- older mother not live long enough to rear infant to survivable age
Usually occurs between ages of 45 and 55
Age of menopause has increased in last century
Menopause considered complete when there has been no menstruation for a year. Evolution says that older mother not live long enough to survivable age
Oogenesis and Sexual Cycle
Reproductive cycle
—sequence of events from fertilization to giving birth and returning to fertility
Sexual cycle what are the two cycles w/in
—events that recur every month when pregnancy does not intervene
Consists of two interrelated cycles controlled by shifting patterns of hormone secretion
Ovarian cycle—events in ovaries
Menstrual cycle—parallel changes in uterus
Oogenesis
—egg production produces haploid gametes by meiosis producing 1 egg per month due to changes in hormone secretion changing histological structure of ovaries in uterus and resulting in monthly menstrual
Embryonic development of ovary-
female germ cells arise from yolk sac colonizing gonadal ridges and differentiate there in the first 5-6 weeks they then differentiate into oogonia multiplying until 5th month reaching 6-7 million in number then are under arrested development until birth. Differentiate into primary oocytes to meiosis I done by birth rest can be called egg or ovum to time of fertilization
atresia
Oocytes undergo atresia process of degeneration so only 2000,000 left by puberty ovulating 480 times, lifetime supply
Egg development resumes
in adolescence, FSH stimulates cohorts to complete meiosis two unequal daughter cells of different size and destinies w/ a lot of cytoplasm needed to keep creating daughter cells of fetus.
Secondary oocytes
products of meiosis proceed as far as metaphase two, arrests until ovulation if not fertilized die and doesn’t finish meiosis completes, if fertilization occurs casts off a polar body, uniting w/ sperm.
Ovarian Follicles- Folliculogenesis–
development of follicle around egg undergoing oogenesis.
Primordial follicles-
primary oocyte in early meiosis surrounded by single layer of squamous follicular cells and basement membrane separated from ovary in ovarian cortex. 13-50 years to develop. 90-95% primordial in adult.
Recruitment primordial follicle
activation awakens 2 dozen primordial follicles each month for a 290 day maturity
Primary follicles-
140 days into cycle larger secondary oocyte than predecessor and follicular cells are simple cuboidal their development is done by recruiting primordial follicles ot become primary.
Secondary follicles-
170 days, oocyte larger multiple layers of cells,
Tertiary follicles
60 days before ovulation, pools enlarge and emerge entrance to form follicles. Mature 20 days before ovulation w/ one becoming follicle destined to ovulate rest die or degenerate. One ovulate captures and holds FSH to ovulate 5 days before ovulation become preovulatory follicle.
Sexual Cycle
- 28 days, hormones of hypothalamus regulate pituitary gland, pituitary regulate ovaries, which in turn regulating uterus. Ovaries exert feedback control of brain.
Sexual cycle begins
Cycle begins two weeks w/in the follicular phase. beginning w/ 3-5 days of menstruation discharge of blood and endometrial tissue. Preovulatory phase- end of menstruation until ovulation. Uterus replaces lost tissue by mitsis, w/ tertiary follicles grow until dominant follicle ovulates around day 14. Remainder of follicle becomes corpus luteum.
FSH stimulates
growth of follicles in cohort particularly dominant to secrete estradiol, which causes it to upregulate receptors w/ rich blood supply becoming preovulatory follicle rest degenerate because estradiol inhibits GnRH decreasing FSH that is picked up more often by dominant.
Ovulation
-day 14 rupture of mature follicle and release of egg and cells surrounding it, estradiol stimulates surge of LH (inducing primary oocyte complete meiosis, follicular fluid swells dramatically, macrophages & enzymes weaken follicular wall releasing egg) and FSH by anterior pituitary, lasting 2-3 minutes. Egg swept up by ciliary currents into uterine tube catches oocyte swelling w/ edema, fimbria grab ovary in synchrony w/ womens heartbeat, cilia create gentle currents in peritoneal fluid, if not caught and fertilized can create ectopic pregnancy
Ovarian Cycle
- reflects what happens in ovaries w/ their relations to hypothalamus and pituitary
Luteal phase (postovulatory)
- corpus luteum stimulates endometrial secretion making it thicker, last two days if not fertilized starts over. (phase—day 15 to day 28, from just after ovulation to onset of menstruation
High levels of estradiol and progesterone, along with inhibin from the corpus luteum, have a negative feedback effect on the pituitary
Corpus luteum begins process of involution (shrinkage)
Ovulation occurs in one ovary per cycle with the two ovaries usually alternating from month to month
Ovulated oocyte began ripening 290 days earlier and began development before birth
Follicle ruptures and collapses bleeding into antrum, clotted blood absorbed
Granulosum and cells surrounding fill antrum there are dense beds of capillaires growing surrounding
Ovulated follicle corpus luteum transformation of ruptured follicle regulated by LH, stimulates grow and secrete rising estradiol and progesterone (crucial roll for preparing for possibility of pregnancy). secretion of FSH and LH decline throughout cycle.
Corpus luteum involution shrinkage 22-26, what was corpus luteum becomes small scar w/ diminishing ovarian steroid secretion FSH levels rise and new follicle starts to develop. Ovulation- One ovary per cycle alternating, oocytes began ripening 290 earlier.
Menstrual cycle
—consists of a buildup of endometrium during most of the sexual cycle, followed by its breakdown and vaginal discharge
Divided into four phases:
proliferative phase,secretory phase,premenstrual phase,and menstrual phase
Proliferative
- rebuilding of functional layer of endometrium lost during last menstruation. thickening as new follicle development secrete more estrogen stimulating mitosis in basal layer of cells regenerating functional cells and blood vessels. Estrogen stimulates Endometrial cells to produce more progesterone receptors
Secreteory
- thickens in response to progesterone from corpus luteum, 16-26, thickened due to secretions of fluid, endometrial glands secrete glycogen wider, larger, longer and more coiled thickening endometrium creating soft wet nutritional environment possible embryonic development
Premenstrual- endometrial degeneration last two days of cycle atrophy falling hormones cause tissue necrosis menstrual cramps interrupting blood flow to endometrium mixing dead endometrium, blood and serous fluid during menstruation
Last 2 days of the cycle/
Corpus luteum atrophies and progesterone levels fall
Triggers spasmodic contractions of spiral arteries
Causes endometrial ischemia (interrupted blood flow)
Brings about tissue necrosis and menstrual cramps
Pools of blood accumulate in the functional layer
Necrotic endometrium mixes with blood and serous fluid: menstrual fluid
Menstrual cycle
-discharge fluid from vagina day 1 of new cycle contains. Contains fibrinolysin so blood doesn’t clot.
Endometriosis-
growth of endometrium in site other than uterus w/ too thick or growth of those cells in peritoneum cavity can cause infertility destroying tissues or blocking things
Female Sexual Response-
similar phases to male.
Excitement and plateau, orgasm, and resolution
excitement and plateau
labia minora becomes congested w/ blood and moves beyond labia majora, which becomes reddened and enlarged spreads away from vagina. serous fluid seeps through walls into vagina, greater vestibular gland provide more lubrication. Lower 1/3 of vagina constricts as the orgasmic platform becoming a narrower canal. w/ rugae enhancing stimulation inducing orgasm in both partners. Upper end dilates and becomes cavernous tenting effect standing vertical. Breast swell and nipples become erect, w/ clitoris erected and is primary focus of sexual stimulation
orgasm
latent plateau phase, many woman experience involuntary pelvic thrusts, followed by 1-2 sets of suspension or stillness preceding orgasm. Orgasm is an intense sensation spreading from clitoris to pelvis w/ pelvic throbbing, spreading sense of warmth, cervix plunges spasmodically into vagina. Uterus exhibit peristaltic contractions drawing semen from vagina, anal and urethral sphincters constrict. Paraurethral glands homologous to prostate expel copious fluid. Tachycardia, hyperventilation, breasts enlarge, areola engorged w/ reddish, rash like flush on lower abdomen, chest, neck and phase.
resolution
uterus drops forward to regular position, orgasm platform relaxes, vagina returns to normal dimensions, flush disappears, nipples undergo rapid back to normal size, start sweating no refractory for woman, can have multiple orgasms
Pregnancy and Childbirth
Gestation (pregnancy)-
Lasts an average of 266 days from conception to childbirth
Gestational calendar measured from first day of the woman’s last menstrual period (LMP)
Birth predicted 280 days (40 weeks) from LMP
Term:the duration of pregnancy
Trimesters:three 3-month intervals in the term
Conceptus
- products of conception, embryo or fetus as well as placenta and membranes
blastocyst
-during first two weeks is a hollow ball; embryo- day 16-week 8; fetus- beginning of week 9 until birth; neonate- first 4 weeks after birth
Attached by umbilical cord to placenta (disc-shaped organ providing nutrition, waste disposal, and hormone secretion regulating pregnancy, mammary development, and fetal development) on uterine wall
Hormones with strongest influence on pregnancy:
All primarily secreted by the placenta (corpus luteum first several weeks, if removed before 7 weeks pregnancy terminates 7-17 degenerate) and their levels are an indicator of the well-being of the fetus.
hcg, estrogen, progesterone, has,
Human chorionic gonadotropin
- secreted by blastocysts and placenta. Present 8-9 days after conception, and it used for pregnancy tests peaking around 10-12 weeks then low throughout rest. Stimulates growth of corpus luteum (w/out it corpus luteum would atrophy and uterus would expel conceptus) doubling it in size and secreting increasing amounts of progesterone and estrogen.
Estrogens-
secreted by corpus luteum increases 30X usual amount by end of gestation, corpus luteum source for 12 weeks, placenta takes over. Causing tissue growth in fetus and mother. Mother: uterus and external genitalia to enlarge, mammary ducts to grow, breasts to increase to twice size, pubic symphysis more elastic, sacroiliac joints more limber widening pelvis during pregnancy
Progesterone
- corpus luteum and placenta. Together w/ estrogen suppresses pituitary secretion of FSH and LH, preventing follicles from developing. Suppresses uterine contractions so conceptus not prematurely expelled. Promotes proliferation of decidual cells of endometrium, on which blastocyst feed, in addition to development of secretory acini in lactation.
Human chorionic somatomammotropin
- higher than all others combined, but not understood. Begins around 5th week increasing till end of term based on size of placenta. In other mammals controls mammary development and lactation. In humans appears to be weak growth hormone, reduce mother’s insulin sensitivity and glucose usage consuming less of it for use by fetus, promoting release of free fatty acids from adipose tissue.
Other hormones or glands affected during pregnancy:
Pituiatry gland grows 50% larger while pregnany increasing thyrotropin, prolactin, and ACTH;
thyroid gland enlarges 50% because of HcG, pituitary thyrotropin, and HcT from placenta
Thyroid hormone-
elevated increasing metabolic rate of mother and fetus.
Parathyroid-
parathyroid glands enlarge stimulating osteoclast activity, liberating calcium from mother’s bones for fetal use
ACTH-
stimulates glucocorticoid secretion, mobiliza amino acids for fetal protein synthesis
Aldosterone-
increase promoting fluid retention, contributing to mother’s increases blood volume
Relaxin-
secreted by corpus luteum and placenta relaxing pubic symphysis in other animals; synergizing progesterone in stimulating multiplication of decidual cells in early pregnancy promoting growth of blood vessels in pregnant uterus
Adjustments to woman’s body:
every system
Digestive:
nausea/Morning sickness (first sign because of reduced intestinal motility because of steroids or causing preference for blander food not as toxic to fetus), constipation (intestinal motility), heartburn (enlarging uterus pressing upward on stomach causing reflux up), metabolic rate increase 15% (overheated from extra weight, hungry)
Nutrition-
higher demand for protein, iron, and calcium than can ingest in late pregnancy so fetus stores it up from beginning to be ready for it. Vitamin K (minimize neonatal hemmorhage0, D (calcium absorption), folic acid (reduce neurological disorders) are all supplements taken by pregnant women
Circulatory system changes from fetus
blood volume rises 30% (fluid retention and hemopoiesis 1-2L), cardiac output rises (30-40$ by 27 weeks fall to normal during last 8 weeks). Pressure on large pelvic blood vessels interferes w/ venous return causing varicose veins, feet swelling, and hemorrhoids,
Respiratory: increased ventilation.
Skin grows to adapt to changing abdomen and breast size and shifting organs w/ squished and growing up to xiphoid process 900g at end of pregnancy 50g not pregnant.
Childbirth-
In the seventh month of gestation, the fetus normally turns into the head-down vertex position
Most babies born head first
Head acting as a wedge that widens the mother’s cervix, vagina, and vulva during birth
Fetus is a passive player in its own birth
Expulsion achieved by contractions of mother’s uterine and abdominal muscles
Fetus may play a role chemically by stimulating labor contractions
Sending chemical messages that signify when it is developed enough to be born
Labor Contractions- Braxton Hick contractions-
weak unterine contractions becoming stronger in late pregnancy sending women to hosital for “false labor,” but at term suddenly transform into labor contractions marking parturition onset of birth
Uterine contractiona-
progesterone decline after 6 months and estradiol rise are a balance producing stronger contractions.
Posterior pituiary secretes oxytocin, increasing receptors, promoting labor by stimulating muscles of myometrium and female membrane to secrete prostaglandins, synergists (prolonged if lacking, induced by OT).
Conceptus stimuli promoting birth. Fetal cortisol rises throughout enhancing estrogen by placenta pituitary produces oxytocin promote prostaglandin secretion.
Uterine stretching of smooth muscle increases contractility particularly when fetus is stretching the cervix.
Labor contractions-
begin 30 minutes apart to 1-3 minutes apart. Intermitent w/ each compressing arteries reducing blood flow so relax to restore flow. Strongest in fundus and body of uterus weaker near cervix pushing downard.
W/ continued oxytocin positive feedback and contractions, woman feels need to bear down, reflex arc from uterus to spinal cord to skeletal muscles causing contraction expells fetus w/ valsalva maneuver.
Positive feedback theory of labor: Labor induced by stretching of cervix, Triggers a reflex contraction of the uterine body, Pushes the fetus downward, Stretches the cervix even more, Self-amplifying cycle of stretch and contraction
Pain in human birth due to
ischemia of myometrium, tearing stretched tissue (widen via episiotomy), from unusually large brain and narrowing of pelvic outlet because of bipedalism.
Stages of Labor-
dilation, expulsion, afterbirth
Dilation stage:
longest stage—lasting 8 to 24 hours. Dilation of cervical canal to 10 cm (size of fetal head) and effacement (thinning) of cervi. Rupture of fetal membranes and loss of amniotic fluid. “Breaking of the waters”
Late dilation—dilation reaches 10 cm in 24 hours or less in primipara(first baby) and in as little as a few minutes in multipara
Expulsion stage
: from entry of head into vagina until baby is expelled, drains umbilical vein, clamps cord, cleans out nose and mouth
30-60 minutes in primipara; shorter in multipara
Crowning—when baby’s head is visible
Delivery of the head is the most difficult part
After expulsion, attendant drains blood from umbilical vein into baby
Umbilical cord is clamped and cut
Placental stage:
uterine contractions cause placental, amion etc. separation
Membranes (afterbirth) inspected to be sure everything has been expelled. Uterus loses 50% of weight in week back to normal in 4 w/ bloody vaginal discharge as cells break up, breastfeeding promotes involution suppressing estrogen secretion (remain flaccid), stimulates oxytocin causing it to contract firming up sooner
Lactation
-the synthesis and ejection of milk from the mammary glands. High levels of estrogen in pregnancy causing ducts of mammary glands to grow and and branch out. Growth hormone, insulin, glucocorticoids, and prolactin also contribute. Once ducts completed progesterone stimulates the budding of ducts and lobules.
Lasts as little as 1 week in women who do not breastfeed their infants
Can continue for many years as long as the breast is stimulated by a nursing infant or a mechanical device (breast pump)
Women traditionally nurse their infants until a median age of about 2.8 years
Colostrum
-thin-watery and cloudy yellow color a secretion formed in late pregnancy distending the acini and ducts. Similar to breast milk in protein and lactose but ⅓ less fat w/ infants sole nutrition for 1-3 days, don’t need high fat or fluid at first contains immunoglobulins IgA resisting digestion protecting infant from gastroenteritis conferring immunity.
Prolactin Secretion in the lactating females-
prolactin promotes milk synthesis, dopamine when not pregnant, beginning 5 weeks into pregnancy 10-20 times normal level full term. Little affect on mammary glands because steroids from placenta acting on mammary glands allow preparation but antagonize prolactin, when placenta discharged these levels drop w/ prolactin secreting effect..
Milk requires:
growth hormone, cortisol, insulin, and parathyroid hormone to mobilize necessary amino acids, fatty acids, glucose, and calcium.
At birth prolactin
drops to pre-birth, when infant nurses jumps 10-20 times for next hour stimulating more milk production for next feeding/ smaller increases in estrogen and progesterone. Prolactin or nerve signals from brain inhibit GnRH rare to become pregnant while breastfeeding. w/out breastfeeding milk stops w/in week.
How is milk found?
Milk secreted into ducts and lobules but doesn’t easily flow, milk ejection controlled by neuroendrocrine reflex from infant suckling on nipple stimualtes hypothalamus and posteior pituitary to secrete oxytocin stimulating myoepithelial cells around each acini contract and squeezing milk into duct 30-60 seconds after suckling.
Composition of milk
changes over first 2 weeks varies throughout day, less lactose and protein 6X the fat. Cows milk is not subsitite1/3 less lactose and more protein more nitrogenous wastes in infant. Milk laxative effect niconium, green of bile filled cleaning out fetus from what was inside womb. Clostrum supplies antibodies and coloinzes, females produce 1.5L each day
embryo
categorized by two cell stage after fertilization or 16 days old w/ 3 primary germ layers w/ previous time period considered pre-embryonic stage where embryogenesis is occurring.
Fertilization
- combines haploid set of sperm and egg chromosomes producing diploid set, has to occur w/in 12-24 hours of ovulation in the distal ⅓ of the uterine tube. It takes 72 hours for the fertilized egg to reach the uterus.
Sperm-
majority of sperm dont make it that far: destroyed by vaginal acid, drain out of the vagina, does not penetrate mucus of cervical canal, those that penetrate destroyed by leukocytes in uterus, go up wrong uterine tube 200 make it out of 300 million. Migrate by snakelike lashing of tails crawling across mucosa.
Female assistance of sperm
- Strands of cervical mucus guide the sperm up through, orgasm causes uterine contractions sucking semen from vagina and spreading it throughout the uterus, egg releases a chemical attractant molecule attracting the sperm from very short distance.
Capacitation
plasma membrane toughened by cholesterol preventing premature release of acrosomal enzymes while still in male avoiding its waste, preventing enzymatic damage to sperm ducts. While the sperm can Reach distal uterine tube in 30 minutes but requires 10 hours to fertilize, because of this. Female fluids leech cholesterol from sperm plasma membrane and dilute inhibittory facctors of semen. Membrane become more fragile and permeable to calcium, diffusing into sperm stimulating more powerful tail lashing.
Sperm are only viable? when should conception occur?
up to 6 days after, conception optimal window a few days before ovulation to 14 hours afterwards.
Acrosomal reaction- Exocytosis of acrosome, release enzymes that penetrate egg clearing path for other sperm penetrating granulosa and zona pellucida usually requiring numerous.
Polyspermy what is it and describe the two mechanisms that prevent it?
- fertilization by two + sperm, causing egg to die of gene overdose prevented by:
Fast block- binding of sperm to egg opening sodium channels depolarization and inhibiting attachment of more sperm w/ an additional slow block causing release of granules creating fertilization membrane
Secondary oocyte
begins Meiosis II before ovulation stopping at metaphase II and only completes it when fertilization. When the second polar body forms it discards one from each promise they then swell becoming pronuclei w/ a mitotic spindle forming between them mixing gametes into diploid set called a zygote beginning to divide
First trimester
fertilization through 12 weeks, ½ of all die because of its vulnerability to stress, drugs, and other susceptible.
Second trimester-
weeks 13-24, organs complete development, can see w/ sonography and by end appears human, can survive toward end w/ intensive care towards end
Third trimester
weeks 25-birth, fetus grows rapidle organs achieve cellular differentiation supporting life outside womb. At around 35 weeks and 5 pounds mature at this weight usually surviving if born early w/ twins born around this time.
Twins: dizygotic and monozygotic
dizygotic- two eggs are ovulated and fertilized by separate sperm as similar as regular siblings with own placenta, which can fuse. Monozygotic- one egg fertilized and splits during cleavage genetically identical very similar, same sex
Preembryonic stage-
first 16 days of development culminating to be an embryo, zygote divides into hundred of cells organizing into primary germ layers, attach to wall, and becoming embryo.
Cleavage
- mitotic division that creates smaller and smaller blastomeres not necessarily increasing in size. first occurs in the first three days while conceptus migrates down uterine tube. First cleavage- occurs w/in 30 hours after fertilization when zygote splits into two daughter cells. producing blastomeres. Conceptus arrives in uterus 72 hours later consisting of 16 cells- morula resembles mulberry. Morula is free in uterine cavity for 4-5 days dividing into 100 cells, zona pellucida disintegrates releasing conceptus, becoming blastocyst.
Blastocyst-
hollow sphere w/ an outer layer of squamous cells- trophoblast become placenta and nourishment of embryo, and inner cell mass, embryoblast becoming embryo, and internal blastocoel cavity.
Implantation
- 6 days after ovulation blastocyst attaches to endometrium on fundus or posterior wall of uterus. Trophoblast attaches to the wall splitting into two layers, the superficial-breaking down walls fuses into multinucleate mass syncytiotrophoblast growing into uterus like roots digesting the cells and deep- cytotrophoblasts retaining individual cells. Endometrium grows over blastocyst covering it burying it in the tissue lasting for a week completing by next menstrual period.
Trophoblasts secrete
human chorionic gonadotropin, stimulating corpus luteum to secrete estrogen and progesterone suppressing menstruation until second month. Trophoblasts develop into chorion which further increases estrogen and progesterone. Ovaries are inactive through the rest of pregnancy from this period.
Embryogenesis:
arrangement of blastomeres into three primary germ layers in the embryoblast ending at 16 weeks once these are formed
Embryoblast separates
slightly from the trophoblast narrow space becoming amniotic cavity. Embryoblast flattens into an embryonic disc initially composed of two layers epiblast- facing abdominal cavity and hypoblast- facing away from abdominal cavity forming yolk sac
Embryo bilaterally symmetrical dorsal and ventral gastrulation-
multiple epiblast cells that migrate medially toward groove and down into it replacing hypoblast w/ endoderm. Migrating epiblasts form third layer between the first two creating the mesoderm. Remaining epiblast is ectoderm all arising from epiblast.
Ectopic Pregnancy-
Blastocysts implants somewhere it’s not supposed to 1/300. Most common are tubule pregnancies occurring because conceptus encounters constriction because of pelvic inflammatory disease, or repeated miscarriages common to have again, as it cannot expand enough to accommodate growing conceptus usually causes Rupture w/in 12 weeks. Abdominal pregnancies where it implants in abdominal cavity can threaten life, w/ therapeutic abortion needed w/ 9% result in live birth by cesarean section.
Embryonic Stage
- All three germ layers present 16 days to over 6 weeks placenta forms on uterine wall becoming embryo’s primary means of nutrition.
Organogenesis
- germ layers undergo differentiation to organs becoming organ system present but not function at 8 weeks.
During week four
while embryo rapidly grows and folds around yolk sac. Goes from a Flat disc becoming cylindrical C shaped w/ head and tail touching. Lateral margins of disc fold around yolk sac forming ventral surface of embryo covered w/ ectoderm becoming epidermis of skin. Mesoderm splits into two layers adhering to ectoderm and endoderm forming coelom dividing into thoracic cavity and peritoneal week 5 developing into pleural and cardiac cavities as well as somites forming vertebral column, trunk muscles, and dermis. Neural tube forms from ectoderm in week 5. 8 weeks all organs present
Ectoderm
- becomes the nervous system, epidermis, hair and cutaneous glands, adrenal, pineal, and pituitary glands, eye, ear, salivary glands, epithelium of nose mouth and anas.
Mesoderm-
skeleton, cardiac, all muscle types, adrenal cortex, middle ear, dermis, blood and lymphatic system, epithelium of kidneys, ureters, gonads, genital ducts mesothelium of abdominal and thoracic cavity.
Endoderm-
mucosal epithelium of digestive, respiratory, excretory, reproductive and digestive glands, thyroid and parathyroid glands and thymus.
Embryonic Membranes-
Accessory organs develop with embryo: placenta, umbilical cord, and four embryonic membranes: amnion-liquid containing sac protecting embryo, yolk sac,allantois-where toxic wastes are stored, and chorion- what it uses to breathe. Yolk sac vs. amniotic sac placenta in outer portion connected by umbilical cord.
Amnion
-transparent sac develops from epiblasts grows to enclose embryo penetrated by umbilical fold, fills w/ amniotic fluid protecting embryo from trauma, infection, and temperature fluctuations allowing it the freedom of movement necessary for muscle development, symmetrically preventing parts from adhering and stimulates lung development to breathe the fluid. Formed from filtration of mother’s blood plasma, but 8-9 weeks fetus urinates in it once an hour contributing to its fluid volume as it swallows it at the same rate.
Yolk sac
- arising from hypoblast cells opposite amnion, small sac suspended from ventral side of embryo contributes to formation of digestive tract, produces first blood cells and future gonad cells.
Allantois-
outpocketing of yolk sac becoming outgrowth of caudal end of gut forming foundation for umbilical cord and part of the urinary bladder
Chorion
- outermost membrane enclosing the rest of membranes and embryo w/ a shaggy outgrowth of villi called villous (fetal portion of placenta) and smooth chorion
Uterine milk-
glycogen-rich secretion of uterine tubes and endometrial glands conceptus absorbing fluid as it travels down tube in uterine cavity before implantation w/ the accumulation forming blastocoel
Trophoblastic/decidual cells of endometrium-
progesterone from corpus luteum stimulates these cells to proliferation and accumulate glycogen, proteins, and lipids. As conceptus burrowing into endometrium syncytiotrophoblast digest these cells supplying the nutrients to embryoblast only mode of nutrition for first week of implantation dominant source through week 8 wanes as placenta takes over ceasing at week 12.
Placental nutrition-
fetus’s life support system, disc-shaped organ attached to uterine wall on one side and on fetus on other by umbilical cord, sole source of oxygen, nutrients, and waste disposal by diffusion of nutrients and waste from and to mother’s blood. Begins dveloping 11 days after conception and dominant mode of nutrition around week 9 w/ sole mode of nutrition from week 12 to birth.
Umbilical cord contains
two 2 arteries and 1 vein, pumped by fetal heart blood flows into placenta by umbilical arteries returning to fetus by vein. Barrier is thin but w/ thick impermeable membranes w/ small surface area as they grow it increases thinning membrane becoming more permeable increased placental conductivity and diffusion rate w/ substance diffusing through membrane. Permeable to nicotine, alcohol, and other drugs.
Fetal Development:
By the end of 8 weeks 3 cm long. head is half body length.
All organ systems are present, w/ organs maturing until birth supporting life outside mother, Heart, beating since week 4, now circulates blood
Skeletal muscles exhibit spontaneous contractions, bones start to calcify
Heart and liver are very large, forming the prominent ventral bulge
The fetus is the final stage of prenatal development-
From the start of week 9 until birth. Full term fetus is 18 inches. 50% of birth weight added in last 10 weeks.
Blood Circulation in the Fetus -
How its different: umbilical- placental circuit and presence of three circulatory shunts.
ductu venosus-
Internal iliac artery gives rise to umbilical arteries passing on either side of bladder into umbilical cord w/ the blood low in oxygen, high in CO2, and fetal wastes. Arterial blood discharges wastes into placenta, loads oxygen, and nutrients that returns to fetus by single umbilical vein leading toward liver. Liver doesn’t perform major functions as it is immature so it is bypassed by ductus venosus into inferior vena cava.
foramen ovale and ductus arteriosis
Inferior vena cava- placental blood mixes w/ venous blood from fetus’s body flowing to right atrium of heart. Fetal blood bypasses pulmonary circuit going directly from right atrium to left through foramen ovale, hole in interatrial septum into right ventricle pumped to pulmonary trunk routed to aorta by ductus arteriosus. Collapsed pulmonary circuit creating high resistance and blood pressure flowing through ductus into aorta toward lower pressure receiving only trickle enough for their needs. Left ventricle enters general systemic circulation returns to the placenta.
neonate
Transitional period of 6-8 hours as the infant has to adapt to life outside as the heart and respiratory rate increase, body temperature falls as physical activity declines and baby sleep for 3 hours. Second period of activity causes gagging on mucus and debris in pharynx, sleeps again, becomes more stable and begins cycle of waking 3-4 hours to feed. First four weeks are neonatal period.
Respiratory stimulation at birth
or CO2 accumulation after birth w/ automatic closure stimulates chemoreceptors, can be depressed by oversedation of the mother, inflating collapsed alveoli, first 2 week 45 breaths per minute, but stabilizes at 12 breaths per minute
Circulatory Adaptations as a neonate-
when lungs expand resistance and blood pressure in pulmonary circuit drop and pressure in right heart is blood that in left flowing from left atrium to right through foramen ovale pushing two flaps of tissue into place closing the shunt allowing these flaps to fuse, doesnt happen in 25% of babies, pressure changes in pulmonary trunk and aorta cause ductus arteriosis to collapse closing around 3 months of age becoming ligamentum arteriosum. After cutting, umbilical artery and vein undergo fibrosis becoming median umbilical ligaments of abdominal wall and vein becoming round ligament of liver, ductus venosus becomes ligamentum venosum on liver.
Immunologic adaptations after birth
Cellular immunity appears in early fetal development, born w/ near adult levels IGG from mother. Breaks down rapidly after birth declining to half initial level in first month and none by 10 months. High enough for 6 months protecting infant from measles, diphtheria, polio, infectious diseases, 6 months igg half adult lowest 5-6 months w/ respiratory infections. igA in colostrum provides breast-fed nenotate protection against gastroenteritis.
Thermoregulation
-infant has a larger ratio of surface area to volume than an adult, lose heat more easily. Brown fat, adipose tissue deposited during week 17-20 of development, releases all energy of pyruvic acids as heat rather than ATP, heat-generating tissue. Metabolic rate increases as it grows accumulating subcutaneous fat producing and retaining more heat. Discovered in human population w/ severe weather decreases and extreme cold as adults have more brown fat then someone else.
Fluid balance-
idneys not fully developed at birth and cannot concentrate urine, w/ a high rate of water loss requiring more fluid.
Systems insignificantly matured for neonate:
liver, joints, myelination of nervous system
Premature Infants-
Infants born before 37 weeks under 5.5 pounds. have multiple difficulties in regard respiratory problems, thermoregulation, excretion, digestion, liver function.
respiratory problems in premature infants
If they are born before 7 months infant respiratory distress syndrome (IRDS), most common cause of neonatal death, alveoli collapse at each exhales w/ great effort needed to inflate becoming fatigued by high energy demand of breathing and can be treated by ventilating lungs w/ oxygen enriched as at a positive pressure to keep them inflated in between breaths administering surfactant as an inhalants, not producing surfactant until develops on own.
brain and digestive issues in premature infants
Hypothalamus undeveloped and can’t regulate thermoregulation. Digestive issues w/ small stomach volume, underdeveloped sucking and swallowing must be fed nasogastric or nasoduodenal tubes, so unable to breastfeed, under 3 pounds requires calcium, phosphorus and protein supplements.
liver issues in premature infants
Immature liver causes hypoproteinemia upsetting capillary filtration and reabsorption leading to edema, bleeding easily because of a lack of clotting factors. Vitamin K injected for help for more clotting factors even full term. Jaundice is common in babes because liver can’t dispose of bile pigments w/ elevated bilirubin level acting as antioxidant.
Birth Defects, or congenital anomalies—
abnormal structures or positions of organs at birth resulting from a defect in prenatal development. Teratology—the study of birth defects.
Not all are noticeable at birth, Some detected months to years later, In most cases the causes of anomalies are unknown
Teratogens what is it? what are the classes and what can happen?
- anatomical deformities in fetus classes: drugs and other chemical, infectious disease, radiation. Effect depending upon genetic susceptibility, dosage, and time of exposure. During first 2 weeks causes no birth defects but instead spontaneous abortion. Greatest vulnerability at 3-8 weeks, w/ different critical periods limbs and brain abnormalities. Many produce less obvious or delayed including physical or mental impairment, inattention, hyperirritability, strokes, seizures, respiratory arrest, crib death, and cancer.
Thalidomide effect on birth defects
prescribed for morning sickness in early pregnancy or a sedative, has severe teratogenic effects on limb development, w/ limbs unformed, ear, heart, and intestinal defects. Avoid sedatives, barbiturates, opiates, acne medication.
Cigarette smoking causes
fetal and ectopic pregnancy, anencephaly(cerebrum failure development), cleft palate and lip, anomalies of the heart.
Alcohol causes
more birth defect than any other drug, with a single drink affect fetal and childhood development not noticeable until school age. Can cause fetal alcohol syndrome (FAS) w/ a small head, malformed facial features, cardiac and central nervous system defects, stunted growth, poor attention span, nervousness, and poor attention span
Microorganisms-
cause stillbirth, neonatal death, and congenital anomalies. Including viral infections such as herpes simplex, rubella, cytomegalovirus, HIV, gonorrhea and syphilis. Mild effects on adults but for fetus can cause: blindness, hydrocephalus, cerebral palsy, seizures, and profound physical and mental retardation.
Genetic anomalies
- ⅓ of all birth defects. Mutations can cause dwarfism, microcephaly, stillbirth, and childhood cancer. Can be caused by genes or mutagens (chemicals, viruses, and radiation), separation of homologous chromosomes during meiosis aneuploidy, presence or lack of an extra chromosome accounts for 50% of spontaneous births
Turner Syndrome
no X chromosome fertilized by X bearing sperm, Y bearing sperm leads to death, 97% die before birth, no serious impairments as children, webbed neck, widely spaced nipples, short. At puberty secondary sex characteristics fail to develop w/ absent ovaries, sterile.
Down Syndrome
Only three trisomies survivable 13, 18 (5% die before first year) & 21 Down Syndrome- 1/800. most survivable, impaired physical and intellectual development, short stature, flat face nasal bridge, low set ears, folded eyes, enlarged protruding tongue, stubby fingers. Outgoing affectionate personalities w/ cognitive impairment common and sometimes severe but not always. 75% died before birth, 20% die before age 10 immune deficiencies and heart and kidney abnormality, but can live to 60 from alzheimer’s. Based more so on aging of eggs for meiosis, defects in mitotic spindle aging eggs less and less ability to separate chromosomes more likely to have a child w/ down syndrome because of aged eggs.
aging
all changes occurring in the body with the passage of time: growth, development, and degenerative changes that occur later in life
senescence
the degeneration that occurs in organ systems after the age of peak functional efficiency/ Gradual loss of reserve capacities, reduced ability to repair damage and compensate for stress, and increased susceptibility to disease
Common diseases associated w/ aging
Heart disease, stroke, cancer, diabetes, and lung disease death of people over 55 as they are related to aging, w/ an unclear cause. Personal health and fitness greatly impacts it, and the senescence of one organ leads to others.
skin changes w/ age
intrinsic aging noticeable by late 40s, gray and thin hair as melanocytes die, mitosis slows causing thinning and hair loss, atrophy of sebaceous glands leads to dry skin, skin becomes paper thin and translucent from mitosis decline and collagen loss, loss of elasticity, fewer blood vessels those remaining are fragile causing easy bruising- rosacea dilated blood vessels on nose and cheeks. Injuries more common and severe in old age because of decline of cutaneous nerve endings by ⅔ from 20-80 years making less aware of touch, pressure, and injury healing slowly from lack of circulation and immune cells. Recurring infection from lack of dedritic cells. Atrophy of all of skin make more vulnerable to hot and cold weather and heat stroke. aging more slowly. Declining vitamin d by 75% causing calcium deficiency bone loss, weakness, and impaired glandular secretion and synaptic transmission
Photoaging-
degenerative changes in proportion to persons exposure to UV rays causing 90% of changes ex. Skin cancer, yellowing of skin, age spots, wrinkling (arms, hands and legs) giving leathery deeply wrinkled appearance w/ malignant cells damage to blood vessels and problems w/ elastic fibers.
Skeleton w/ aging
after 30 osteoblasts less active than osteoclasts, osteoporosis losing bone mass, brittle w/ less protein, fracture easier and heal longer, synovial fluid less abundant, osteoarthritis, difficulty breathing because of restricted expansion of thorax by calcification. Women over 40 lose 8% each decade, men 3%. Hip broke and then fell.
Muscular responses to aging
atrophy from not moving around as much, replacement of muscle w/ fat. active helps lessen all. Muscular strength and mass peak in 20s half that by 80. Fast twitch exhibit earliest and most severe atrophy, increasing reaction time and reducing coordination. Muscle fibers have less myofibrils, smaller mitochondria myoglobin, fewer nutrients, more fat limiting motion. Fewer motor neurons and less efficient synaptic transmission, slower, less efficient blood flow to muscles causing rapid fatigue, slow healing, and scar tissue.
Nervous system changes w/ age
age 30 peak, losing 5% every decade, giri narrower, sulci wider more space in between causing fewer synapses, less neurotransmitters & receptors, degeneration of myelin, slowing down signals, motor coordination, and these are biggest changes fastest loss in prefrontal cortex including abstract thought, judgment, planning, personality, and explicit memory. ANS- loses adrenergic receptors and loss of control of homeostasis. Drop in blood pressure when standing resulting in dizziness, loss of balance, or fainting
Sense organs changing w/ age
- vision loss- decline in the flexibility of lenses, cataracts-cloudiness in lens night vision impaired fewer receptors, pupil dilators atrophy, slower photoreceptors, change in eye structures. Hearing- ossification different parts of ear causing deafness as ossicle joints stiffen. Hair cells and auditory nerve fibers decline w/ death of vestibular neurons causing dizziness. Olfactory bulbs and neurons decline bluting taste.
Endocrine changes w/ age
ages least except reproductive, target-sensitivity declines w/ age. Prolonged stress response pituitary less sensitive to feedback from adrenal, diabetes because of high fat
Circulatory changes w/ age
–anemia from poor nutrition and lack of exercise. Less B12 absorption, kidney age decreasing nephrons less erythropoietin, atherosclerosis degeneration of myocardium, angina pectoris, and myocardial infarction, heart walls are thinner and weaker, stroke volume and cardiac output decline, less conductive heart nerves causing arrhythmia and heart block, weakening of arteries causing aneurysm and stroke, varicose veins and blockages.
Lymphatic and immune changes w/ aging
decline in red bone marrow and lymphatic tissue, fewer leukocytes, APCs, lymphocytes less protected against cancer and infectious diseases.
Respiratory changes w/ aging
costal cartilage and joints less flexible, elasticity, and alveoli. Less capable of clearing lungs of irritants, pathogens more easily infections such as pneumonia.
Urinary changes w/ age
loss of nephrons, filtration is decreased, less efficient at clearing wastes, less responsive to ADH causing dehydration, have to reduce drug doses in old age as they are cleared less. Men develop prostatic hyperplasia, and woman weak pelvic muscles both lead to incontinence.
Digestive changes w/ aging
reduced appetite, smaller stomach, loss of taste, reduced saliva making swallowing difficult, damage to dentition from salvia, less active, reduced absorption of calcium, iron, zinc, and folic acid, heartburn from weakening valve, constipation reduced muscle tone and weaker peristalsis reduce muscularis externa, nerve sensitivity, less fiber and water.
Digestive changes w/ aging
reduced appetite, smaller stomach, loss of taste, reduced saliva making swallowing difficult, damage to dentition from salvia, less active, reduced absorption of calcium, iron, zinc, and folic acid, heartburn from weakening valve, constipation reduced muscle tone and weaker peristalsis reduce muscularis externa, nerve sensitivity, less fiber and water.
Reproductive changes w/ aging
- loss of sperm count by 65 lost ⅓. Impotence from atherosclerosis, hypertension, medication, and psychological. Woman: less labido, increased osteoporisis vaginal dryness
Exercise and Senescence
Good nutrition and exercise are best ways to slow senescence
Quality of life, maintains endurance strength and joint mobility, reduce incidences and severity of hypertension, osteoporosis, and diabetes, 90 year old increase muscle strength 3 fold in 6 months w/ isometric exercise.
resistance and endurance exercises what do they do to help halt senescence?
Resistance Exercise reduces bone fractures Endurance exercises reduce body fat and increase cardiac output and oxygen uptake, 3-5 20-60 minutes per week increasing 60-90% maximum heart rate Improves
Why do organs wear out?
Senescence- may be intrinsic process governed by inevitable or even programmed changes in cell function
Senescence may be due to extrinsic (environmental) factors that progressively damage our cells over a lifetime damage cells, hereditary factors can play a role such as genetic conditions.
Death
Some organ functions after heart stops. Braindeath lack of cerebral activity lack of heartbeat or respiration 30-60 minutes other organ failure multiple thignsfailing
Life expectancy
—average length of life in a given population
Has increased substantially over the last century. Today in U.S.: Average boy can expect to live 76.2 years, Average girl can expect to live 81 years
Life span
—maximum age attainable by humans
Has not increased for many centuries
No recorded age beyond 122 years
Theories of senescence
Certain theories involve replicative senescence so the decline of mitotic potential w/ age as the organ depends on cell renewal keeping pace w/ cell death, but cells can only divide a limited number of times because telomeres, end of DNA protect DNA from degradation and damage during mitosis dictating that each cell can only replicate a certain number of times. As they are exhausted this makes chromosomes more vulnerable to DNA damage and replication errors causing old cells to be less functional, w/ thousands of damaging events per day, oxidative stresses from free radicals generated by metabolism, most is repaired but some persists and accumulates hurts function, foe example ¼ of bodies protein collagen w/ age these molecules become less soluble and more stiff of joints lenses in eye and arteries. Protein abnormalities abnormal structures in tissue and cells, changes to shape and molecule accumulate w/ more abnormal proteins w/ age. Autoimmune theory- altered macromolecules cause lymphocytes against them causing autoimmune diseases w/ age. Natural selection genes of reproductive rate, genes that don’t affect this will not be favored or eliminated allowing things like alzheimer’s and atherosclerosis to persist as it is passed reproductive age w/ no effect on genes.
