Reproductive System Physiology Overview

Mitosis

A type of cell division resulting in two daughter cells, each with the same number of chromosomes (diploid) as the parent.

Meiosis

Cell division producing four genetically unique haploid cells, important in gamete formation.

Spermiogenesis

Final stage of spermatogenesis where spermatids mature into sperm.

Spermatogenesis

Entire process of sperm cell development (mitosis → meiosis → spermiogenesis).

Chromosome

DNA structure carrying genetic material; humans have 46 (23 pairs).

Chromatid

One of two identical halves of a replicated chromosome.

Haploid

A cell with half the number of chromosomes (n = 23).

Diploid

A cell with the full set of chromosomes (2n = 46).

Oogenesis

Formation of female gametes (ova).

Follicle

Structure in ovaries containing a developing oocyte and surrounding cells.

Polar body

A small cell produced during oogenesis that eventually degenerates.

Ovulation

Release of a secondary oocyte from a mature follicle.

Fertilization

Fusion of sperm and ovum to form a zygote.

Menses

Menstrual bleeding due to shedding of the uterine lining.

Proliferative

Phase of the uterine cycle where the endometrium rebuilds.

Spermatozoa

Mature sperm cells.

GnRH

Hormone from hypothalamus that stimulates the anterior pituitary.

FSH

Hormone that acts on Sertoli cells to promote spermatogenesis.

LH

Hormone that stimulates interstitial (Leydig) cells to release testosterone.

Testosterone

Final trigger for spermatogenesis; regulates male traits.

Male Infertility

Often due to low sperm count, poor motility, or hormone imbalances.

Oogonia

Cells that complete mitosis before birth.

Primary oocytes

Arrested in prophase I until puberty.

Ovulated secondary oocyte

Arrests in metaphase II until fertilization.

Fertilization

Triggers completion of meiosis II.

Follicular Phase

Follicle growth → mature Graafian follicle → ovulation.

Luteal Phase

Corpus luteum forms → degenerates if no fertilization.

Menses

Shedding of endometrium.

Proliferative Phase

Endometrial regrowth under estrogen.

Secretory Phase

Glands secrete nutrients under progesterone.

GnRH

Stimulates FSH & LH release.

Estrogen

Endometrial repair, secondary sex characteristics.

Progesterone

Maintains endometrium; secreted by corpus luteum.

Birth Control

Prevents ovulation by maintaining hormone levels (estrogen/progesterone) artificially.

Difference between mitosis and meiosis

Mitosis produces 2 diploid identical cells; meiosis produces 4 haploid genetically unique cells.

Effect of low FSH on sperm production

Reduced FSH impairs spermatogenesis, lowering sperm count.

Functions of interstitial and nurse cells

Interstitial (Leydig): Produce testosterone. Nurse (Sertoli): Support, nourish developing sperm, form blood-testis barrier.

Source, target, effect of GnRH in males

Source: Hypothalamus; Target: Anterior pituitary; Effect: Stimulates FSH and LH release.

FSH and LH targets/effects in males

FSH: Sertoli cells → sperm production; LH: Interstitial cells → testosterone production.

Stages of spermatogenesis

Spermatogonium (2n) → primary spermatocyte (2n) → secondary spermatocytes (n) → spermatids (n) → spermatozoa (n).

Oogenesis vs. spermatogenesis

Oogenesis produces 1 ovum + 3 polar bodies; occurs monthly; starts before birth. Spermatogenesis produces 4 sperm; continuous from puberty.

Primary, growing, tertiary follicles

Primary: Single layer of cells around oocyte. Growing: Layers increase, fluid begins accumulating. Tertiary (Graafian): Fully mature, ready to ovulate.

Follicular vs. postovulatory phase (ovary)

Follicular: Follicle grows; estrogen rises. Postovulatory: Corpus luteum forms; progesterone dominates.

Uterine cycle phases

Menses: Endometrial shedding; Proliferative: Endometrium rebuilds; Secretory: Endometrium thickens/secretes nutrients.

Blockage of progesterone receptors in uterus

Prevents endometrium maintenance → possible early shedding or failed implantation.

Event with low estrogen/progesterone

Menses begins (menstrual bleeding).

How birth control alters hormones/cycle

Maintains steady estrogen/progesterone → prevents LH surge → no ovulation or follicle maturation.