(Mostly) The Male Reproductive System

Chapter 27 Part I

The Reproductive System

Body function that allows for the production of offspring

Gametes

Mature haploid cells — sperm and ova (egg)

Copulation

The act of sexual intercourse or mating — brings together the sperm and egg

Fertilization

The act of combining the genetic content of the sperm and the egg

Gestation

The period of time from conception to birth during which a baby develops within the mother’s womb

Parturition

The action of giving birth to young; childbirth — in labor

Meiosis

Nuclear division that occurs only in the gonads and results in the formation of gametes

• Reduces the number of chromosomes in gametes by half

  • Produces genetic variability

Sister Chromatids

Replicated chromosomes before meiosis occurs

• Identical copies of a single chromosome, joined at a region called the centromere

Homologous Chromosomes

Matching pairs of chromosomes, one from each parent, that carry the same set of genes in the same order

Meiosis I Result

2 haploid daughter cells

Haploid Cell (n)

Cell that has a single set of chromosomes

• Ex. gametes

Diploid Cell (2n)

Cell that contains two sets of chromosomes, one from each parent

• Ex. human cells

Meiosis II Result

4 haploid daughter cells

Prophase I

Crossing over occurs

Metaphase II

Tetrads align randomly on spindle plate

Anaphase I

Homologous chromosomes separate and move to opposite poles

• Sister chromatids DO NOT separate

Telophase I

Cleavage occurs, resulting in 2 haploid daughter cells

Prophase II

Formation of new spindle

Metaphase II

Chromosomes line up at equator

Anaphase II

Sister chromatids separate and move to opposite poles

Telophase II

Cleavage occurs, resulting in 4 haploid daughter cells

Hypothalamic-Pituitary-Gonadal (HPG) Axis

The interaction of hormone released by the hypothalamus, anterior pituitary, and gonads

• Regulate hormone production and release → regulates gamete formation

Hypothalamus

Structure that releases gonadotropin-releasing hormone (GnRH)

Anterior Pituitary Gland

Structure that released follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to GnRH presence

Gonads

Structure that release sex hormone and produce gametes in response to LH and FSH

Female Gonads

Release estrogen and progesterone

Male Gonads

Release testosterone

Gonadotropin-Releasing Hormone (GnRH)

Hormone that travels to and stimulates the pituitary gland to release LH and FSH

• Increase during puberty, triggering the onset of sexual maturation

Follicle-Stimulating Hormone (FSH)

Hormone wherein:

• In females, stimulates the development of ovarian follicles and egg production

• In males, essential for sperm production

Luteinizing Hormone

Hormone wherein:

• In females, triggers the ovulation and stimulates the production of estrogen and progesterone

• In males, stimulates testosterone production

Testis

Male primary reproductive organ that produces sperm; male gonad

Scrotum

Layer of skin and superficial fascia that encloses and protects the testes

• Allows testes to be outside the abdominopelvic body cavity, making them ~3º lower than internal body temperature (important for sperm production)

Dartos Muscle

Muscle of scrotum that changes surface area of scrotal tissue

• When contracted, reduces the surface of the scrotum → reduces heat loss

Cremaster Muscle

Muscle of the scrotum that changes the position of the testes

• When contracted, pulls the testes up and closer to the abdominopelvic cavity → prevents drastic decrease in temperature

Testicular Arteries

Paired vessels that supply blood to each testicle

Testicular Veins

Paired vessels that drain blood from the testicles

• Temperature regulation — absorb some heat

Testis Sympathetic Division

When activated, decrease sperm formation

Testis Parasympathetic Division

When activated, increase sperm formation

Spermatic Cord

Cord-like structure in the male reproductive system that carries the ductus deferens, blood vessels, nerve fibers, and lymphatics

Seminiferous Tubules

Location of sperm production → inside the walls

Rete Testis

Network of tubules in the testicle that transports immature sperm to the epipdidymis

Seminoma

Testicular cancer where the tumor is slowly growing, non-aggressive

• Easier to treat

Non-Seminoma

Testicular cancer where the tumor grows much more quickly, more aggressively

Epididymis

Tightly coiled tube attached to the back of each testicle, stores immature sperm

• Where sperm mature before being released into ductus deferens

Ductus Deferens (vas deferens)

Muscular tube in the male reproductive system that transports sperm out of epididymis during ejaculation

Ampulla (of DD)

Widened section of the vas deferens at the bladder’s base, the end of the vas deferens

Ejaculatory Duct

Short, paired tube in the male reproductive system that carries sperm and seminal fluid from vas deferens to urethra

• Ampulla ends here

Vasectomy

Procedure that involves the cutting or cauterizing of the ductus deferens

• Reversible, but not 100% effective

• Not immediately effective, takes 2-3 months

Urethra

Canal through which urine passes from the bladder to outside the body

• In males, semen passes through here from the ejaculatory duct—terminal portion of male duct system

Prostatic Urethra

Portion of the urethra that is surrounded by the prostate gland

Intermediate Part of the Urethra

Part of the urethra that connects the prostatic urethra and the spongy urethra, travels through the body wall

Spongy Urethra

Portion of the urethra that runs through the penis and opens to the exterior of the body

Penis

Male reproductive organ that delivers sperm to female reproductive tract during copulation

Glans

The sensitive, rounded tip of the penis “head” — the end of the penis

• Surrounded by prepuce

Prepuce

Commonly known as the foreskin, can be removed via circumcision

Erectile Tissue

Tissue responsible for maintaining an erection that contains connective tissue, smooth muscle, and vascular space (which fills with flood)

Corpus Spongiosum

Erectile body of the erectile tissue that immediately surrounds the urethra

• Distal portion forms glans

Corpora Cavernosa

Erectile body of the erectile tissue that contains paired structures (left and right) that make up most of the penile tissue

Seminal Glands

Paired accessory glands of the male reproductive system that empty into ejaculatory duct — combines the sperm here

• Secretions produced: fructose, prostaglandins, proteins

Prostate

Accessory gland of the male reproductive system that is composed of 20-30 glands

• Produces citrate, PSA, and substances that help activate sperm

  • Smooth muscle walls contract during ejaculation to release contents

Prostate-Specific Antigen (PSA)

Immunoglobulin that breaks down certain components of semen to make it more fluid in nature (makes it easier for semen to leave the body)

Prostate Cancer

Type of cancer that develops in the small gland located below the bladder in men, causing difficulty in urinating, blood in urine and/or semen, erectile dysfunction, etc.

• 1 in 6 men will develop this, usually later in life (age 50+)

• Usually die with it, not because of it

Benign Prostatic Hyperplasia

Age-associated prostate gland enlargement wherein the cells divide too quickly (they are normal non-cancerous cells, but do cause an increase in size)

• Constricts prostatic urethra, making urination difficult and painful

Bulbo-Urethral Glands

Two pea-sized accessory glands of the male reproductive system that produces alkaline mucus to neutralize the acidity of sperm traveling through the urethra

Semen

The combination of sperm with accessory gland secretions

Prostaglandins

Seminal secretion that decreases viscosity of mucus in female cervix, stimulates reverse peristalsis in uterus

• Carries more of an effect in the female reproductive system, where it makes it easier for sperm to travel to the uterus by pushing it up

Relaxin

Seminal secretion wherein, along with other enzymes, promotes and enhances sperm motility

• When exposed to enzymes, sperm swims faster

Fructose

Seminal secretion that is catabolized by sperm for ATP synthesis

Antibiotic Components

Seminal secretion that destroys bacteria that could harm sperm

Clotting Factors

Seminal secretion that coagulates sperm after ejaculation to prevent the quick leaving of sperm from the female body

Other Secretions from Semen

Seminal secretions that suppress the immune system of the female reproductive system → female immune system will recognize semen as foreign and will try to destroy it

Spermatogenesis

Production of male gametes

Sustenocytes

Cell type of seminiferous tubules that surround, support, and nourish developing sperm

• Joined by tight junctions → prevent sperm from escaping

Spermatogenic Cells

Sperm-forming cell types of seminiferous tubules

Myoid Cells

Cell type of the seminiferous tubules that contract to move immature sperm from tubules to the epididymis

Interstitial Endocrine Cells

Cell type of the seminiferous tubules who secrete testosterone (with small amount of estrogen)

Spermatogonia

Primitive male germ cells in the testes that give rise to sperm

• Divide by mitosis

Type A Daughter Cells

After puberty, continue to become spermatogonia

Type B Daughter Cells

After puberty, become primary spermatocytes

Secondary Spermatocytes

Formed from primary spermatocytes, these cells form spermatids

Spermatids

Undergo spermiogenesis

Spermiogenesis

The final stage of sperm cell formation, where round spermatids transform into elongated spermatozoa

Sperm Head

Area of sperm that holds genetic material

Acrosome

Helmet-like structure of the sperm head that holds hydrolytic enzymes

Sperm Midpiece of

Metabolic area of the sperm that contains mitochondria

• ATP powers motility

Sperm Tail

Locomotor region of the sperm with flagellum

Male Luteinizing Hormone

Stimulates interstitial endocrine cells of testes to secret testosterone

Male Follicle-Stimulating Hormone

Stimulates sustenocytes to release androgen-binding protein (ABP)

Androgen-Binding Protein

Keeps local testosterone levels in testes high

Hypothalamic-Pituitary-Gonadal (HPG) Axis

Key endocrine system that regulates reproductive functions in both males and females — crucial for fertility and sexual development

• Each stimulate each other one after another, primarily works after puberty

Temporary Surge

Fetus has this of gonadotropins and testosterone before birth to stimulate the development of the reproductive organs

• Drops, and does not appear again until puberty

Secondary Sex Characteristics

Features induced in non-reproductive structures due to influence of sex hormones

Nitric Oxide

Chemical that vasodilates blood vessels supplying erectile tissue

• Male arousal causes the parasympathetic system to stimulate the release of this

Erection: Corpora Cavernosa

When filled, compresses drainage vessels → prevents blood from leavingE

Erection: Corpus Spongiosum

When filled, pinches off the urethra → prevents semen from leaving the body

• Fills, but not as much as the other

Ejaculation

Propulsion of semen from the duct system, caused by initiation of spinal reflex

Internal Sphincter of Bladder

Closes during ejaculation to prevent the release of urine being passed with semen

Bulbospongiosus Muscles of Pelvis

Contract rapidly to propel semen out of the body during ejaculation