Block 5.1-2

Male reproductive system — Lecture 5.1

What are the 4 major parts of the male reproductive system?

Testes, ducts, accessory sex glands, and supporting structures.

Function of testes?

Produce male gametes/sperm and hormones.

Function of ducts in the male reproductive tract?

Store and transport sperm.

Function of accessory sex glands?

Add secretions to form semen.

Function of supporting structures?

Support/protect reproductive organs; examples include penis and scrotum.

What are germ cells?

Cells that become gametes; sperm in males and eggs/oocytes in females.

What are Sertoli cells?

“Nurse cells” that support developing sperm in the seminiferous tubules.

Main role of Sertoli cells?

Support sperm production and help sperm mature/move toward the lumen.

Sertoli cells are connected by what structure?

Tight junctions.

What do tight junctions between Sertoli cells form?

The blood-testis barrier.

What is the blood-testis barrier?

A selective barrier separating blood components from developing germ cells.

Why is the blood-testis barrier important?

It protects developing sperm and creates a controlled environment for spermatogenesis.

What happens if Sertoli cells are nonfunctional?

Sperm development is impaired, which can cause infertility.

What are Leydig cells?

Sex-steroid-producing cells found between seminiferous tubules.

What hormone do Leydig cells synthesize?

Testosterone.

What hormone stimulates Leydig cells?

LH.

What hormone stimulates Sertoli cells?

FSH.

What does FSH promote in males?

Spermatogenesis through actions on Sertoli cells.

What does FSH stimulate Sertoli cells to produce?

Androgen-binding protein and inhibin.

Function of androgen-binding protein, ABP?

Keeps local testosterone concentration high near developing sperm.

What does inhibin do?

Provides negative feedback to decrease FSH release.

What is the basic HPG axis for male gamete formation?

Hypothalamus releases GnRH → anterior pituitary releases LH and FSH.

LH acts on what cell?

Leydig cells.

FSH acts on what cell?

Sertoli cells.

What does testosterone do in spermatogenesis?

Supports and stimulates sperm production.

How does testosterone give negative feedback?

It inhibits LH release through the hypothalamus/anterior pituitary pathway.

What enzyme converts testosterone to estradiol?

Aromatase.

Why is estrogen important in males?

It helps sperm maturation and supports cartilage and bone growth.

What is spermatogenesis?

The full process of making sperm: spermatogonium → spermatozoa.

Where does spermatogenesis occur?

In the seminiferous tubules of the testes.

What are spermatogonia?

Stem cells that give rise to sperm.

What type of division maintains spermatogonia numbers?

Mitosis.

Type A spermatogonia do what?

Stay near the outside edge and maintain the germ line.

Type B spermatogonia do what?

Move toward the lumen and commit to sperm production.

Correct order of spermatogenesis?

Spermatogonium → primary spermatocyte → secondary spermatocyte → spermatid → spermatozoon.

Primary spermatocyte chromosome number?

Diploid = 46 chromosomes.

Secondary spermatocyte chromosome number?

Haploid = 23 chromosomes, but chromosomes are still duplicated.

Spermatid chromosome number?

Haploid = 23 chromosomes, chromatids separated.

Mature spermatozoon chromosome number?

Haploid = 23 chromosomes, carrying either X or Y.

What happens during meiosis I in spermatogenesis?

Primary spermatocyte becomes secondary spermatocytes; chromosome number is reduced.

What happens during meiosis II in spermatogenesis?

Chromatids separate to produce spermatids.

What is spermiogenesis?

Differentiation of spermatids into mature sperm.

What forms during spermiogenesis?

Flagellar tail, acrosome, and mitochondrial sheath.

What is spermiation?

Release of mature spermatozoa from Sertoli cells into the seminiferous tubule lumen.

What is capacitation?

Final maturation/activation of sperm in the female reproductive tract.

What triggers capacitation?

Secretions from the uterus/female reproductive tract.

Before capacitation, can sperm fully fertilize the egg?

No; it cannot fully penetrate the egg.

After capacitation, what can sperm do?

Swim strongly, bind to the egg, undergo the acrosomal reaction, and release acrosome enzymes.

What is hyperactivation?

Stronger tail movement after capacitation.

What is the acrosome?

Cap on the sperm head containing enzymes to digest the outer protective layers of the ovum (zona pellucida) for fertilization

Function of acrosome?

Helps sperm penetrate the oocyte.

What does the sperm nucleus contain?

23 highly condensed chromosomes.

Why is sperm DNA highly condensed?

To protect genetic material.

What is the mitochondrial sheath/midpiece?

Region containing mitochondria that produce ATP for tail movement.

Function of sperm tail?

Propels sperm forward.

Major function of testosterone?

Supports spermatogenesis, protein anabolism, and skeletal muscle growth.

How is testosterone carried in blood?

Bound to albumin and sex hormone-binding globulin, SHBG.

Testosterone can be converted to what stronger androgen?

DHT.

DHT contributes to what?

Prostate growth.

What is BPH?

Benign prostatic hyperplasia, enlargement of the prostate gland with age.

Is BPH cancer?

No, it is benign enlargement.

Why does BPH cause urinary problems?

Enlarged prostate squeezes the urethra and makes urine harder to leave the bladder.

Common BPH symptoms?

Difficulty starting urination, frequent urination, overflow incontinence, and feeling the bladder is not empty.

What is PSA?

Prostate-specific antigen test.

What is PSA used for?

To help rule out/check for prostate cancer, but effectiveness is variable.

Parasympathetic nervous system causes what in male sexual function?

Erection.

Sympathetic nervous system causes what in male sexual function?

Ejaculation.

Memory for parasympathetic vs sympathetic in erection?

Parasympathetic = point; sympathetic = shoot.

How does parasympathetic signaling cause erection?

Penile arterioles dilate, blood enters erectile tissue, veins compress, and blood stays trapped.

What erectile tissue fills with blood during erection?

Corpora cavernosa.

Parasympathetic signaling also stimulates which gland?

Bulbourethral glands.

What do bulbourethral glands release?

Alkaline mucus-like pre-ejaculate for lubrication.

What happens during sympathetic signaling after climax?

Ejaculation occurs, penile arterioles constrict, blood leaves, and penis returns flaccid.

Female reproductive system — Lecture 5.2

What are the major parts of the female reproductive system?

Supporting structures, accessory glands, ovaries, ducts, and uterus.

Function of the clitoris?

Sexual stimulation; erectile tissue homologous to the penis.

Function of ovaries?

Produce oocytes and hormones.

Function of ovarian ducts and ovarian tubes?

Transport ova and provide location for fertilization/implantation pathway.

What are female gametes called?

ovum

What is the ovary cortex?

Outer region of the ovary where follicles develop.

What is the ovary medulla?

Middle/inner region of the ovary.

What is an ovarian follicle?

Structure containing an oocyte and surrounding follicular cells.

What does each follicle contain?

An oocyte and follicular cells.

What is oogenesis?

Production and maturation of female gametes/oocytes.

When does oogenesis begin?

During in-utero development before birth.

Primordial germ cells become what in females?

Oogonia.

Oogonia divide by what process?

Mitosis.

Oogonia develop into what?

Primary oocytes.

Primary oocytes are arrested where?

Arrested in prophase I until puberty.

How many oocytes are present at birth?

About 1–2 million.

How many oocytes remain at puberty?

About 300,000–400,000.

How many oocytes usually mature and ovulate in reproductive life?

About 400–500.

What happens each month after puberty?

Several follicles begin maturing, usually one becomes dominant.

What does the primary oocyte complete before ovulation?

Meiosis I.

Primary oocyte completing meiosis I produces what?

A secondary oocyte.

What is ovulation?

Release of the secondary oocyte from the ovary.

If fertilization occurs, what happens?

Secondary oocyte completes meiosis II and becomes part of a zygote.

What is a zygote?

Diploid first cell of human development.

If fertilization does not occur, what happens to the oocyte?

The oocyte dies.

What is atresia?

Degeneration of ovarian follicles that do not fully mature or ovulate.