Chapter 26 - Reproduction and development Flashcards
What are the gonads, internal genitalia, and external genitalia?
The gonads (ovaries, testes) produces gametes, so sperm and eggs The internal genitalia consist of glands and ducts connecting the gonads to the external environment The external genitalia are all external reproductive structures
IN the absence of a Y chromosome, an embryo will develop into a ……….
female
What are Sertoli cells? Their function? What do they secrete?
Sertoli cells are elongated cells in the seminiferous tubules. The nourish spermatocytes. They secrete anti-mullerian hormone causing the regression of the mullerian ducts
What are Leydig cells? Their function? What do they secrete?
Leydig cells are clusters of epitheliod cells in the testis. They are endocrine cells secreting androgens, testosterone and DHT
What is the function of DHT( dihydroxytestosterone)?
It promotes development of the prostate gland and the external genitalia
Describe female embryonic development; in the absence of ………., the mullerian ducts develop into the vagina, uterus, and fallopian tubes. The wollfian ducts ……….. without testosterone
testosterone, regress
What do the Wolffian ducts form? Under influence of which hormone are the wolffian ducts?
The epididymis and vas deferens, testosterone
What do the mullerian ducts develop into? Under influence of which hormone?
They become the fallopian tubes, uterus, cervix, and upper vagina. Under the influence of AMH(anti-mullerian hormone)
Testicular development doesn’t/does require testosterone?
Doesn’t
What are the 4 general steps of gametogenesis?
- Spermatogonia and oogonia undergo mitosis to increase their numbers
- the germ cells DNA replicates until each chromosome is duplicated, forming primary spermatocytes and oocytes
- one primary gamete divides into two secondary gametes, making secondary spermatocytes or oocytes (in females one secondary oocyte, the first polar body) (in males two identical secondary spermatocyte)
- The second meiotic division seperates the sister chromatids
What are the 5 steps of male gametogenesis, starting at the birth?
- At birth, sperm are not past mitosis
- At puberty, spermatogonia have two fates, some keep performing mitosis, others become primary spermatocytes
- primary spermatocytes divide into two secondary spermatocytes
- each secondary spermatocyte divides into two spermatids
- spermatids mature into sperm
What are the 5 steps of female gametogenesis?
- oogonia complete mitosis resulting in primary oocytes
- In puberty, a primary oocyte develops into a secondary oocyte and the first polar body. The first polar body disintegrates
- if the secondary oocyte is selected for ovulation, the second meiotic division takes place just before the egg is released from the ovary
- if the egg is not fertilized, meiosis never completes
- if fertilization takes place, the secondary oocyte is split into the fertilized egg and the second polar boyd
what are the three main steroid sex hormones?
estrogen, progesterone, and androgens (testosterone, DHT)
What is the function of aromatase with regards to hormones?
Aromatase converts androgens to estrogens
What does FSH do?
FSH regulates gametogenesis in the gonads
What does LH do?
LH stimulates production of steriod sex hormones
What do inhibin and activin do? Where are they produced?
Inhibins inhibit FSH secretion, inhibiting gametogenesis. Produced in the sertoli cells and granulosa cells under influence of FSH
Activin stimulates FSH secretion, produced in the gonads, pituitary, and placenta
What is the hormonal pathway controlling reproduction? Name the hormone and where it is secreted, starting from the first and ending in the final hormone of the pathway
Kisspeptin - hypothalamus under influence CNS
GnRH - hypothalamus
LH & FSH from anterior pituitary
LH controls peptide and steroid hormone production in gonads
What happens when estrogen rises rapidly above threshold for over 36 hours? What does it stimulate/inhibit?
THe feedback loop becomes positive. Estrogen starts stimulating the release of gonadotropin
What is the condition called cryptochidisim?
The failure of one or both testes to descend
What 3 structures are the male accessory glands?
- prostate gland
- seminal vesicles
- bulbourethral glands
What is the function of the seminiferous tubules and what cells do they contain?
The tubulues are the site for sperm production in males. They contain sperm cells and sertoli cells
What is the function of sertoli cells? What do they secrete?
Sertoli cells regulate sperm development. they produce inhibin, activin, growth factors, enzymes, and androgen-binding protein
What are the two sites of testosterone production? How much of testosterone is produced where?
95% is produced in the Leydig cells
5% is produced in the adrenal cortex
What are the five functions of testosterone?
- promote spermatogenesis
- maintains accessory organs
- contributes to muscle growth
- influence secondary sexual characteristics
- provides feedback to pituitary/hypothalamus
What does FSH stimulate in the Sertoli cells?
It stimulates the sertoli cells to produce androgen binding proteins, inhibin, and paracrine molecules
What are the three phases of the ovarian cycle? What happens in the phases?
The follicular phase, in which there is follicular growth
Ovulation, in which the oocyte is released from the follicle
Luteal phase, period in which the corpus luteum prepares the body for pregnancy by continuining hormone secretion
What are the three phases of the uterine cycle? What happens in the phases?
- Menses, in which there is menstrual bleeding from the uterus
- proliferative phase, in which the endometrium adds a new layer of cells in the uterus anticipating pregnancy
- secretory phase, in which the thickened epithelium is converted into a secretory structure under the influence of the hormones from the corpus luteum
What is the hormonal pathway controling the uterine and ovarian cycle? From where are they secreted? Start at the hypothalamus
GnRH from hypothalamus
FSH and LH from anterior pituitary
Estrogen, progesterone, inhibin, AMH from ovary
What has to happen for a sperm to fertilize an egg? describe the three steps
- the sperm must penetrate the cells and zona pellucida surrounding the egg
- the sperm binds to the egg through sperm-binding receptors
- binding of the sperm gives rise to a cortical reaction excluding other sperm
What happens after the cortical reaction inside the fertilized egg?
The sperm nucleus moves into the egg cytoplasm
the oocyte nucleus completes meitotic division
the sperm and egg nuclei form a zygote nucleus, a second polar body is expelled and degraded
Why does the corpus luteum remain active after fertilization, and what does it do?
it remains active because of the presence of HcG produced by the embryo/placenta.
HcG stimulates the corpus luteum to keep producing progesterone to keep the endometrium intact
What does the placenta do once developed, around week 7 of development?
It takes over progesterone production from the corpus luteum, and secretes estrogen, progesterone, and human placental lactogen
What are the two main functions of progesterone during pregnancy?
It maintains the endometrium, and helps suppress uterine contractions
What does placental lactogen (HPL) do?
It helps stimulate the mammary glands and stimualtes energy supply to the fetus
What is the hormonal pathway that controls labour? Which hormones are secreted and where?
CRH - placenta
ACTH- fetal anterior pituitary
cortisol- fetal adrenals
oxytocin - maternal pituitary
How is prolactin controlled?
By prolactin-inhibiting hormone. The levels drop during late pregancy, allowing prolactin to work
What is the let-down reflex, and what signal is required for the let-down relfex?
The let-down reflex is the ejection of milk from the mammary glands. It requires the release of oxytocin from the maternal posterior pituitary
Why deos the reproductive cycle in females end, resulting in menopause?
The ovaries can no longer respond to gonadotropins, stopping uterine and ovarian cycle
What is the feedback loop necessary for parturition of the baby?
- The fetus drops lower in the uterus
this causes cervical stretch
Cervical stretch stimulates oxytocin release and uterine contractions
oxytocin stimulates prostaglandin release from the uterine wall, stimulating uterine contractions
uterine contractions stimulate the cervical stretch
uterine contractions eventually cause the delivery of the baby, stopping the cervical stretch signal
What is done in tubal ligation and vasectomy?
Tying off and cutting of the fallopian tube
tying off and clipping of the vas deferens
