Chapter 17 (Human Reproduction) Flashcards
1
Q
Organs of the Male Reproductive System
A
- testes, suspended outside abdominal tract in skin-covered sac called the scrotum
- seminal vesicles
- prostate gland
- bulbourethral gland
- penis
- epidiymis
- vas deferns
- ejaculatory duct
- urethra
2
Q
Testes
A
- descent is usually complete by a the seventh month of gestation
- location of the scrotum provides a cooler environment essential for spermatogenesis
- produces sperm within the seminiferous tubules
- secretes testosterone in interstitial (leydig) cells that lie in the connective tissue between the seminiferous tubules
3
Q
Spermatogenesis
A
- process where undifferentiated diploid cells (spermatogonia) are converted into haploid spermatozoa (sperm)
3 major steps
- mitotic proliferation
- sperm-forming daughter cells divides mitotically twice more to form four identical primary spermatocytes - meiosis
- each primary spermatocyte forms two secondary spermatocytes. after the second meiotic division, there are four spermatids
- 16 spermatozoa result from each spermatogonium that goes through the process - packaging
- spermiogenesis
4
Q
Spermatozoa
A
- remains closely associated with sertoli (nurse) cells throughout development
4 parts
- head
- contains the nucleus/dna - Acrosome
- enzyme filled vesicle that caps tip of the ehad
- used to penetrate the ovum
- formed by endoplasmic reticulum and golgi complex before the organelles are discarded - Midpiece
- mitochondria are concentrated here - Tail
- provides mobility for spermatozoa
5
Q
Semen
A
- average volume 2.75 ml
- ranges from 2-6 ml, typically higher volumes following periods of abstinence
sperm count:
- average ejaculation contains 180 million sperm (66 million/ml)
- can have up to 400 million
- males with less than 20 million /ml are considered infertile
6
Q
Sertoli Cells
A
- forms blood-testes barrier
- provides noursihemnt
- phagocytic funciton
- secretes seminiferous tubule fluid which flushes released sperm from the tubules into the epididymis for storage and additional processing
- secretes androgen-binding protein
- site of action to control spermatogenesis: releases inhibin and acts in negative-feedback fashion to regulated FSH secretion
7
Q
Epididymis
A
- stores and concentrates sperm
- increases sperm motility and fertility prior to ejaculation
8
Q
Seminal Vesicles
A
- supplies fructose for energy
- supplies prostaglandins which promote smooth muscle motility in both male and female reproductive tracts
- provies more than half the semen
- secretes fibrinogens (makes sperm clot)
9
Q
Prostate Gland
A
- contributes alkaline fluid that neutralizes acidic vaginal secretions
- provides clotting enzymes and fibrinolysin
10
Q
Bulbourethral Galnd
A
- releases lubricating mucosa
11
Q
Sexual Response Cycle
A
- Excitement phase
- erection and heightened sexual awareness - Plateau phase
- steadily increasing heart rate, blood pressure, respiratory rate and muscle tension - Orgasmic phase
- ejaculation and other responses that are collectively experienced as intense physical pleasure and heightened emotions - Resolution phase
- return of genitalia and body systems to pre arousal state
12
Q
Female Responses to Sexual Cycle
A
- Excitement
- swelling of labia and erection of clitoris due to parasympathetically induced vasocongestion
- nipples and breasts enlarge i size
- release of mucus (bartholin’s gland) causes lubrication - plateau
- uterus raises upward, lifting the cervix and enlarging the upper 2/3 of the vagina. creates space for ejaculation to be deposited
- physical relaxation - orgasm
- contraction occurs most intensely in the engorged lower third of the vagina
- females can experience 12 successive orgasms - resolution
- pelvic vasocongestion and systemic manifestation gradually subside
13
Q
Ovaries
A
- primary female reproductive organs
- produce ova (oogenesis)
- secretes female sex hormones
14
Q
Estrogen
A
- essential for ova maturation and release
- establishment of female secondary sexual characteristics
- essential for transport of sperm from vagina to fertilization site in the oviduct
- contribution to breast development in anticipation of lactation
- promotes the growth of the myometrium
- development of mammary ducts within the breasts
- enlargement of external genitalia
during pregancy:
- fetal adrenal cortex produces DHEA, which is converted into estrogen, until the placenta develops
15
Q
Progesterone
A
- promotes the growth and maintenance of the endometrium
- suppresses the uterine contractions to prevent miscarriage
- promotes the mucus plug formation in the cervix
- contributes to breasts’ ability to produce milk
- ## converts the endometrium into a highly vascularized, glycogen-filled tissue
16
Q
Oogenesis
A
- takes 12-50 years to complete on a cyclic basis from onset of puberty until menopause
- female has a limited supply of germ cells
- each primary oocyte yields only one cytoplasm rich ovum and 3 cytoplasm poor polar bodies
17
Q
Oogonia
A
- undifferentiated primordial germ cells in fetal ovaries
- divide mitotically and give rise to 6-7 million oogonia by the 5th month of gestation
- during the last part of fetal life, the first meiotic division occurs
- now known as primary oocytes (diploid)
- can remain in meiotic arrest for years until they are prepared for ovulation
18
Q
Primary Oocyte
A
- surrounded by a single layer of granulosa cells
- oocyte + granulosa cells = primary follicle
19
Q
Primary Follicle
A
- after development starts there are two possible fates
- reach maturity and ovulate
- degenerate to form scare tissue (atresia)
- between puberty and menopause, follicles develop into secondary (antral) follicles on a cyclic basis
20
Q
Ovarian Cycle
A
- follicular phase
- dominated by presence of maturing follicles - luteal phase
- characterized by the presence of the corpus luteum
21
Q
Follicular Phase
A
- first half of the cycle
- granulosa cells of primary follicles proliferate
- oocyte inside each follicle enlarges
- Theca cells in follicles secrete an increased amount of estrogen
- rapid follicular growth continues throughout the phase
- one follicle grows more rapidly and matures about 14 days after onset. follicle ruptures to release oocyte from ovary - ovulation
22
Q
Luteal Phase
A
- last 14 days of ovarian cycle
- old follicular cells undergo structural transformation to form a corpus luteum
- becomes highly vascularized
- becomes fully functional within 4 days after ovulation
- continues to increase in size for another 4-5 days
- if released ovum is not fertilized and does not implant, the corpus luteum degenerates about 14 days after formation
23
Q
Hormonal Interactions
A
Follicular Phase
- rise in FSH signals ovarian follicle to secrete more estrogen
- rise in estrogen feeds back to inhibit FSH secretion. it declines as the phase progresses
- LH rises and peaks mid-cycle during ovulation
Luteal Phase
- estrogen output decreases and the follicle is converted into a corpus luteum
- corpus luteum secretes progesterone and estrogen
- progesterone output inhibits release of FSH and LH
- low LH - corpus luteum degenerates
- progesterone levels decline, FSH can start to rise again, initiating a new cycle
24
Q
Uterine Cycle
A
- Menstrual Phase
- Proliferative Phase
- Secretory or Progestational Phase
25
Q
Menstrual Phase
A
- characterized by the discharge of blood and endometrial debris from the vagina
- first day of menstruation is considered start of new cycle
- coincides with the end of ovarian luteal phase and the onset of the follicular phase
- release of uterine prostaglandin which: causes the vasoconstriction of endometrial vessels, disrupts blood supply, causes death of endometrium, stimulates mild rhythmic contractions of the uterine myometrium to help expel blood and endometrial debris
26
Q
Proliferative Phase (LH Surge)
A
- begins concurrent with last portion of ovarian follicular phase
- endometrium starts to repair itself and proliferate under the influence of estrogen and newly growing follicles
- estrogen dominant proliferative phase lasts from end of menstruation to ovulation
- peak estrogen levels trigger LH surge responsible for ovulation
27
Q
Secretory / Progestational Phase
A
- uterus enters this phase after ovulation when a new corpus luteum is formed
- corpus luteum secretes a large amount of progesterone and estrogen
- endometrial glands actively secrete glycogen
- if fertilization and implantation does not occur: the corpus luteum degenerates and a new follicular phase and menstrual phase begins once again
28
Q
Fertilization
A
- oviduct/fallopian tube is site of fertilization. normally in upper third of oviduct (ampulla)
- must occur within 24 hours of ovulation
- sperm can usually survive about 48 hours but can survive up to 5 days
- factors that assure successful transport of the sperm to the egg
1. contractions of the myometrium
2. upward contractions of oviduct smooth muscles
3. allurin released by mature eggs - once sperm reaches the ovum, a chemical change occurs that makes the outer layer impermeable to any more sperm
- plasma membrane of sperm produces protein fertilin (olfactory receptor hRO17-4) that binds to ovums cell membrane protein ZP3, causing a fusion
- hRO17-4 responds to smell of ovum
29
Q
Implantation
A
- fertilized ovum divides mitotically until it becomes a blastocyst that is capable of implantation
- blastocyst implants in the endometrial lining using enzymes released by trophoblasts
- the enzymes carve a hole in the endometrium for implantation, and they release nutrients from endometrial cells to be used by the developing embryo
30
Q
Placenta
A
- develops after implantation
- organ of exchange between maternal and fetal blood
- acts as transient, complex endocrine organ that secretes pregnancy hormones
1. human chorionic gonadotropin - maintains the corpus luteum until the placenta takes over function in the last two trimesters
2. estrogen - essential for maintaining normal pregnancy
3. progesterone - essential for maintaining normal pregnancy
31
Q
Gestation
A
physical changes:
- uterine enlargement
- breasts enlarge and develop ability to produce milk
- volume of blood increases 30%
- weight gain
- respiratory activity increases about 20%
- urinary output increases
- kidneys excrete additional wastes from fetus
- nutritional requirements increase
32
Q
Partuition
A
- labour, delivery, birth
requires: - dilation of the cervical canal
- contraction of uterine myometrium
changes before parturition
- uterus remains quiet and inactive during the first two trimesters
- high progesterone levels exert inhibitory effects on uterine muscles
- in the third trimester, the uterus becomes more excitable to initiate mild contractions “braxton hicks”
- closed cervix keeps the uterus sealed
- initiation of parturition and the hormone relaxin causes the cervix to soften
33
Q
Relaxin
A
- relaxin is produced by the corpus luteum and placenta
- relaxin relaxes the pelvic ligaments for parturition
34
Q
Prostaglandin
A
- promotes cervical enzyme production
- these enzymes degrade collagen fibers which help to soften the cervix
35
Q
Oxytocin
A
- hypothalamus synthesizes
- posterior pituitary stores it
- travels through the blood
causes
- powerful uterine muscles contractions
- increases uterine responsiveness x100
- increased oxytocin receptors in the myometrium for a strong endometrial contraction (critical threshold)
36
Q
Corticotropin Releasing Hormone
A
- fetal placenta creates CRH
- CRH determines the onset of labor, and promotes fetal lung maturation
- stimulates the pituitary gland to secrete ACTH which increases the amount of cortisol and DHEA
- cortisol stimulates the synthesis of pulmonary surfactant. increases lung expansion and reduces the work of breathing
37
Q
Stages of Labor
A
- Cervical dilation
- longest stage, cervix can dilate to 10-12cm - Delivery of the baby
- lasts 30-90 minutes - Delivery of the placenta
- shortest stage, 15-30 minutes
38
Q
Lactation
A
Prolactin:
- stimulates the synthesis of enzymes essential for milk production by alveolar epithelial cells
- withdrawal of placental steroids at parturition initiates lactation. sustained by suckling
- triggers release of oxytocin and prolactin
Oxytocin:
- causes milk ejection by stimulating cells surrounding alveoli to squeeze secreted milk out through ducts
