The Reproductive System 2. Environmental Needs: For spermatogenesis to occur, The Hypothalamus and Pituitary Gland: Orchestrators of
- The reproductive system is vital for reproduction, the germ cells need a specific environment, including: Reproduction
which is the creation of offspring. ● Hormones Two key areas regulate spermatogenesis:
- In humans, this involves sexual reproduction with ● Nutrients
both male and female parents. ● Electrolytes 1. Hypothalamus: Releases gonadotropin-releasing
- Each parent contributes a gamete (sex cell), a haploid ● Enzymes hormone (GnRH).
cell containing 23 chromosomes. Hormonal Control: The Negative Feedback Loop 2. Pituitary Gland (specifically the anterior pituitary):
- Fertilization occurs within this system, leading to the Releases follicle-stimulating hormone (FSH)and
The body uses a negative feedback loop to maintain
development of the zygote and subsequent embryo. luteinizing hormone (LH).
homeostasis in spermatogenesis.
Functions of the Reproductive System - Negative Feedback Loop: A mechanism where a series The Negative Feedback Loop in Action
● Producing gametes of hormones affect each other to maintain balance in 1. Low Sperm Count: If the body detects a drop in
● Producing sexual hormones: the body. sperm count, the hypothalamus releases more GnRH.
○ Testosterone and androgens in males If sperm count drops, the body increases the rate of 2. FSH Release: GnRH stimulates the anterior pituitary
○ Estrogen and progesterone in females spermatogenesis by stimulating Sertoli cells and Leydig cells to to release FSH.
● Transporting and storing gametes produce more testosterone and facilitate sperm production.
3. Sertoli Cell Activation: FSH travels through the blood
● (In females) Developing the embryo and facilitating Conversely, if there's an overproduction of sperm, the body can
to the testicles and binds to receptors on Sertoli
fertilization and implantation decrease the rate.
cells.
4. Androgen-Binding Protein (ABP): Binding of FSH
triggers Sertoli cells to release androgen-binding
Male Reproductive System protein (ABP).
The male reproductive system can be viewed from lateral (side) 5. Testosterone Concentration: ABP binds to
and posterior perspectives. Key organs include the testicle testosterone (produced by Leydig cells),
(primary organ), scrotum, epididymis, various glands, penis, and concentrating it around the germ cells, which
urethra (secondary organs). stimulates spermatogenesis.
Spermatogenesis: The Making of Sperm 6. LH and Leydig Cells: LH from the anterior pituitary
Spermatogenesis is the process by which sperm cells are binds to receptors on Leydig cells, prompting them to
produced. Here's the breakdown: produce more testosterone.
7. Inhibin Release: Sertoli cells also release a hormone
1. Germ Cells: These are the cells that undergo
called Inhibin.
spermatogenesis.
8. Feedback to Hypothalamus: Inhibin travels in the
● They go through meiosis, a type of cell
blood and signals the hypothalamus to reduce the
division, and then maturation to become
release of GnRH, helping to regulate the rate of FSH
sperm cells.
and LH production.
● They must always be available, so they
continuously undergo mitosis to maintain a Regulation of Spermatogenesis
reservoir. ● FSH (follicle-stimulating hormone) directly regulates
● The process includes meiosis I and meiosis spermatogenesis via Sertoli cells.
II, resulting in haploid cells. ● Testosterone is always needed, but its production
● The cells mature into spermatozoa, or increases when spermatogenesis needs a boost.
sperm cells.
, 3. Decreased GnRH deactivates the anterior pituitary, ● Testosterone, estrogen, and progesterone work
Classification of Male Reproductive System: reducing FSH production and release. together to affect libido (sex drive), erection, and
4. This ultimately decreases the rate of ejaculation.
Primary Reproductive Primary Reproductive spermatogenesis.
Seminiferous Tubule Structure
Organs (Gonads) Organs (Genitals/external) The above mechanism is called a negative feedback loop.
Testes → Produces gametes - Testes This mechanism also exists in females, impacting X-cell A cross-section of a seminiferous tubule reveals two main
(sperms) & hormones. - Penis layers and a central lumen.
production, maturation, ovulation, and fertilization.
Secondary Reproductive - Scrotum
organs: Secondary Reproductive Testicle Structure And Function ● Germinal Epithelial: Contains germ cells and Sertoli
- Epididymis Organs (Ducts & Glands): cells.
- Ducts: (Transport The testicle is enclosed within a membrane called the tunica.
- Vas Deferens ● Lumen: Central space where sperm cells are produced
- Seminal Vesicles sperm/fluid) ● Tunica: A membrane surrounding the testicle, primarily and undergo partial maturation. Sperm cells are then
- Prostate Gland Vas Deferens
made of connective tissue and a small layer of transported to the epididymis for complete
- Penis Epididymis
- Urethra epithelial tissue (mesoderm). maturation and motility.
Urethra
- Scrotum - Glands: (They form ○ Provides support and protection.
Cells within the Seminiferous Tubules
- Bulbourethral Semen) ○ Consists of two layers:
- Germ Cell: Undergo meiosis to produce sperm cells;
gland Seminal Vesicles ■ Tunica vaginalis: Outer layer with
high reservoir due to daily sperm production (2-3
Prostate Gland two sublayers:
Bulbourethral million per day).
● Parietal layer: Outer
Gland
sublayer of the tunica
vaginalis.
● Visceral layer: Inner
sublayer of the tunica
vaginalis.
● A fluid-filled space
between these layers
provides lubrication.
■ Tunica albuginea: Inner layer
surrounding the functional units
of the testicle.
● Lobules: Functional areas within the testicle.
Negative Feedback Loop
○ Each lobule contains seminiferous tubules.
To decrease spermatogenesis Seminiferous Tubules: Folded tubes within the lobules
when production is too high: where spermatogenesis and hormone production
1. Inhibin is released occur. Each testicle contains around 500 seminiferous - Sertoli Cells.
by Sertoli cells. tubules. - Leydig Cells
2. Inhibin affects the Androgen Hormones
hypothalamus, ● Testosterone is the primary androgen in males.
decreasing the ● Estrogen is also present in males, produced in the Sertoli Cells: Guardians of Fertility
release of GnRH testes, adipose tissue, and brain. Sertoli cells are crucial for fertility because they provide the
(gonadotropin-releasing hormone). necessary environment for spermatogenesis.
- The reproductive system is vital for reproduction, the germ cells need a specific environment, including: Reproduction
which is the creation of offspring. ● Hormones Two key areas regulate spermatogenesis:
- In humans, this involves sexual reproduction with ● Nutrients
both male and female parents. ● Electrolytes 1. Hypothalamus: Releases gonadotropin-releasing
- Each parent contributes a gamete (sex cell), a haploid ● Enzymes hormone (GnRH).
cell containing 23 chromosomes. Hormonal Control: The Negative Feedback Loop 2. Pituitary Gland (specifically the anterior pituitary):
- Fertilization occurs within this system, leading to the Releases follicle-stimulating hormone (FSH)and
The body uses a negative feedback loop to maintain
development of the zygote and subsequent embryo. luteinizing hormone (LH).
homeostasis in spermatogenesis.
Functions of the Reproductive System - Negative Feedback Loop: A mechanism where a series The Negative Feedback Loop in Action
● Producing gametes of hormones affect each other to maintain balance in 1. Low Sperm Count: If the body detects a drop in
● Producing sexual hormones: the body. sperm count, the hypothalamus releases more GnRH.
○ Testosterone and androgens in males If sperm count drops, the body increases the rate of 2. FSH Release: GnRH stimulates the anterior pituitary
○ Estrogen and progesterone in females spermatogenesis by stimulating Sertoli cells and Leydig cells to to release FSH.
● Transporting and storing gametes produce more testosterone and facilitate sperm production.
3. Sertoli Cell Activation: FSH travels through the blood
● (In females) Developing the embryo and facilitating Conversely, if there's an overproduction of sperm, the body can
to the testicles and binds to receptors on Sertoli
fertilization and implantation decrease the rate.
cells.
4. Androgen-Binding Protein (ABP): Binding of FSH
triggers Sertoli cells to release androgen-binding
Male Reproductive System protein (ABP).
The male reproductive system can be viewed from lateral (side) 5. Testosterone Concentration: ABP binds to
and posterior perspectives. Key organs include the testicle testosterone (produced by Leydig cells),
(primary organ), scrotum, epididymis, various glands, penis, and concentrating it around the germ cells, which
urethra (secondary organs). stimulates spermatogenesis.
Spermatogenesis: The Making of Sperm 6. LH and Leydig Cells: LH from the anterior pituitary
Spermatogenesis is the process by which sperm cells are binds to receptors on Leydig cells, prompting them to
produced. Here's the breakdown: produce more testosterone.
7. Inhibin Release: Sertoli cells also release a hormone
1. Germ Cells: These are the cells that undergo
called Inhibin.
spermatogenesis.
8. Feedback to Hypothalamus: Inhibin travels in the
● They go through meiosis, a type of cell
blood and signals the hypothalamus to reduce the
division, and then maturation to become
release of GnRH, helping to regulate the rate of FSH
sperm cells.
and LH production.
● They must always be available, so they
continuously undergo mitosis to maintain a Regulation of Spermatogenesis
reservoir. ● FSH (follicle-stimulating hormone) directly regulates
● The process includes meiosis I and meiosis spermatogenesis via Sertoli cells.
II, resulting in haploid cells. ● Testosterone is always needed, but its production
● The cells mature into spermatozoa, or increases when spermatogenesis needs a boost.
sperm cells.
, 3. Decreased GnRH deactivates the anterior pituitary, ● Testosterone, estrogen, and progesterone work
Classification of Male Reproductive System: reducing FSH production and release. together to affect libido (sex drive), erection, and
4. This ultimately decreases the rate of ejaculation.
Primary Reproductive Primary Reproductive spermatogenesis.
Seminiferous Tubule Structure
Organs (Gonads) Organs (Genitals/external) The above mechanism is called a negative feedback loop.
Testes → Produces gametes - Testes This mechanism also exists in females, impacting X-cell A cross-section of a seminiferous tubule reveals two main
(sperms) & hormones. - Penis layers and a central lumen.
production, maturation, ovulation, and fertilization.
Secondary Reproductive - Scrotum
organs: Secondary Reproductive Testicle Structure And Function ● Germinal Epithelial: Contains germ cells and Sertoli
- Epididymis Organs (Ducts & Glands): cells.
- Ducts: (Transport The testicle is enclosed within a membrane called the tunica.
- Vas Deferens ● Lumen: Central space where sperm cells are produced
- Seminal Vesicles sperm/fluid) ● Tunica: A membrane surrounding the testicle, primarily and undergo partial maturation. Sperm cells are then
- Prostate Gland Vas Deferens
made of connective tissue and a small layer of transported to the epididymis for complete
- Penis Epididymis
- Urethra epithelial tissue (mesoderm). maturation and motility.
Urethra
- Scrotum - Glands: (They form ○ Provides support and protection.
Cells within the Seminiferous Tubules
- Bulbourethral Semen) ○ Consists of two layers:
- Germ Cell: Undergo meiosis to produce sperm cells;
gland Seminal Vesicles ■ Tunica vaginalis: Outer layer with
high reservoir due to daily sperm production (2-3
Prostate Gland two sublayers:
Bulbourethral million per day).
● Parietal layer: Outer
Gland
sublayer of the tunica
vaginalis.
● Visceral layer: Inner
sublayer of the tunica
vaginalis.
● A fluid-filled space
between these layers
provides lubrication.
■ Tunica albuginea: Inner layer
surrounding the functional units
of the testicle.
● Lobules: Functional areas within the testicle.
Negative Feedback Loop
○ Each lobule contains seminiferous tubules.
To decrease spermatogenesis Seminiferous Tubules: Folded tubes within the lobules
when production is too high: where spermatogenesis and hormone production
1. Inhibin is released occur. Each testicle contains around 500 seminiferous - Sertoli Cells.
by Sertoli cells. tubules. - Leydig Cells
2. Inhibin affects the Androgen Hormones
hypothalamus, ● Testosterone is the primary androgen in males.
decreasing the ● Estrogen is also present in males, produced in the Sertoli Cells: Guardians of Fertility
release of GnRH testes, adipose tissue, and brain. Sertoli cells are crucial for fertility because they provide the
(gonadotropin-releasing hormone). necessary environment for spermatogenesis.
