Chapter 27 The reproductive system

Question 1

Define Meiosis. Compare and contrast it to Mitosis

Answer 1

Two cell divisions and four daughter cells produced, produces gametes. Whereas mitosis no pairing of homologous chromosomes occurs, associated with growth and asexual reproduction, and two daughter cells produced. They both involve the duplication of chromosomes

Question 2

Explain synapsis and crossover and which stage of meiosis this occurs in.

Answer 2

synapsis refers to the homologous chromomosomes coming close together. Crossing over refers to the breakage and rejoining of segments of non-sister chromatids during prophase after bivalents are formed.
happens in prophase 1.

Question 3

Outline the events of spermatogenesis

Answer 3

• Spermatogenesis begins when the spermatogonia divide to produce type A daughter cells that maintain the stem cell line, and type B daughter cells that get pushed toward the lumen to become primary spermatocytes and ultimately sperm.
• Each primary spermatocyte undergoes meiosis I to produce two secondary spermatocytes, which then undergo meiosis II to form spermatids.
• Spermiogenesis is a streamlining process that strips the spermatid of excess cytoplasm and forms a tail, resulting in a sperm with a head, a midpiece, and a tail.
• The sustentacular cells, or Sertoli cells, form a blood-testis barrier that prevents membrane-bound antigens from escaping into the bloodstream.

Question 4

layers of endometrium and their responsiveness to hormones

Answer 4

The inner layer, called the endometrium, is the most active layer and responds to cyclic ovarian hormone changes; the endometrium is highly specialized and is essential to menstrual and reproductive function
The middle layer, or myometrium, makes up most of the uterine volume and is the muscular layer, composed primarily of smooth muscle cells
The outer layer of the uterus, the serosa or perimetrium, is a thin layer of tissue made of epithelial cells that envelop the uterus

Question 5

describe the process of oogenesis and compare it to spermatogenesis.

Answer 5

oogenesis is the process of formation of a mature female gamete. It occurs in the ovaries. It consists of three phases: multiplication, growth and maturation.

Spermatogenesis is the process of formation of sperms. it occurs in the seminiferous tubules of the testes. it includes formation of spermatids and formation of spermatozoa.

Question 6

describe ovarian cycle phase and relate them to events of oogenesis.

Answer 6

The ovarian cycle is the monthly series of events associated with the maturation of the egg.

1. The follicular phase is the period of follicle growth typically lasting from days 1 to 14.
2. Ovulation occurs when the ovary wall ruptures and the secondary oocyte is expelled.
3. The luteal phase is the period of corpus luteum activity, days 14–28.

Question 7

describe the regulation of the ovarian and uterine cycles

Answer 7

Hormonal Regulation of the Ovarian Cycle
•During childhood, the ovaries grow and secrete small amounts of estrogen that inhibit the release of GnRH until puberty, when the hypothalamus becomes less sensitive to estrogen and begins to release GnRH in a rhythmic manner.

Hormonal Interactions During the Ovarian Cycle
•On day 1 of the cycle, levels of GnRH rise and stimulate increased production and release of FSH and LH.
•FSH and LH stimulate follicle growth and maturation, and estrogen secretion.
•Rising levels of estrogen in the plasma exert negative feedback on the anterior pituitary, inhibiting release of FSH and LH.
•Estrogen exerts positive feedback on the anterior pituitary, resulting in a burst of LH triggering ovulation and transforming the ruptured follicle into the corpus luteum.
•Rising plasma levels of progesterone and estrogen exert negative feedback on LH and FSH release.
•LH levels fall and luteal activity ends; the corpus luteum degenerates, dropping the levels of estrogen and progesterone, and the cycle starts again.

The uterine (menstrual) cycle is a series of cyclic changes that the uterine endometrium goes through each month in response to changing levels of ovarian hormones in the blood 
•The menstrual phase takes place on days 1–5 typically, and is the time when the endometrium is shed from the uterus. 
•The proliferation phase (days 6–14) is the time in which the endometrium is rebuilt, once again becoming velvety, thick, and well vascularized. 
•The secretory phase (days 15–28) is the phase in which the endometrium prepares for implantation of an embryo.