Male Reproductive System

Unit 3

Male reproductive system purpose

Produce, store, nourish, and transport gametes

Gonads

Reproductive organs that produce gametes and hormones

Male reproductive ducts

* Receive and transport gametes
* Connected to chambers and passageways (which together form the reproductive tract)

Spermatic cords

* Extend between abdominopelvic cavity and scrotum
* Encloses ductus deferent, blood vessels, nerves, and lymphatiscs

Scrotum

Fleshy pouch

Inguinal canal

Canals form as testes descend into scrotum during development

Lobules

Septa of testes divide into these

Seminiferous tubules

Sperm production takes place here and merge into straight tubules

Straight tubules

Interconnected in maze called the rite testis, connected to epididymis via efferent ductules

Interstitial endocrine cells (Leydig cells)

* Located in spaces between seminiferous tubules


* Responsible for androgen production of dominant sex hormones

Androgen

Androsterone and testosterone

Sperm is transported into epididymis via _____

Cilia

Epididymis

Start of the male reproductive tract of coiled tube attached to the posterior border of each testis

Efferent ductules

Head of epididymis receives sperm from efferent ductules

Ductus deferens

* Ascends through inguinal canal into abdominal cavity
* Connects with seminal glands and prostate near bladder to enter urethra

Epididymis functions

1. Monitors and adjusts composition fluid
2. Recycles damaged sperm
3. Stores and protects sperm

Ductus deferens walls

Contain smooth muscle for peristaltic contractions

Inactive sperm with low metabolic rate can be _____________ for months

Stored in ductus deferens

Urethra

* Passageway extending from urinary bladder to tip of penis
* Used in both urinary and reproductive systems

Accessory gland examples

Seminal glands, prostate, bulbo-urethral glands

Accessory gland purpose

* Activating sperm
* Prodviding nutrients needed for motility
* Propelling sperm/fluids along reproductive tract via peristalsis
* Producing buffers to counteract acidity of urethra and vagina

Seminal glands (seminal vesicles)

* Ductus deferens end at duct that drains into the seminal glands
* Tubular glands with extensive epithelial folds
* Produce majority of semen and empty into the ejaculatory duct

Ejaculatory duct

Penetrates the muscular wall of prostate and empties into the prostatic urethra

Prostate

* Small, muscular, round organ
* Circles urethra as exits bladder
* Prostate glands produce prostatic fluid

Prostatic fluid

* 25-30% of semen
* Slightly acidic, rich in enzymes to prevent sperm from clotting in the vagina
* Ejected into urethra by peristaltic contractions

Bulbo-urethral glands (Cowper’s glands)

* Located at penis base
* Secrete thick, alkaline mucus that neutralizes urinary acids and lubricates penis tip

Semen contents

* Sperm (20-100million per 1ml of semen)
* Seminal fluid (alkaline mixture of glandular fructose)
* Enzymes (protease, seminalplasmin, fibrinolysin)

Semen ejaculation amount

2-5mL

Root of penis

Fixed portion attached to body wall

Body of penis

* Shaft, tubular, moveable portion
* Made of 3 cylindrical columns of erectile tissue

Glans penis

Head, expandable distal end with skin resembling the scrotum as a continuation of dartos

Foreskin/prepuce

Surrounds tip of penis, attached to neck

Preputial glands

Secrete waxy material called smegma

Cylindrical columns of erectile tissue

1. Copora cavernosa
2. Copora cavernosa (2 layers)


1. Corpus spongiosum

Flacid penis

Erectile tissue is relaxed

Erect penis

Erectile tissue is dialated

Spermatogenesis

* Process of sperm formation
* Puberty-past age 70
* 64 days to complete

Spermatogonia

* Stem cells in seminiferous tubules that divide by mitosis into 2 daughter cells
* One daughter cell moves toward lumen of tubule and differentiates into **primary spermatocyte**
* Begin meiosis I to become secondary **spermatocyte**
* Differentiate by meiosis II into immature **spermatids**

Nurse cells

Spermatocytes and spermatids undergoing spermatogenesis surrounded by cytoplasm of __________

Functions nurse cells (Sertoli cells)

1. Maintain blood-testis barrier
2. Support mitosis and meiosis
3. Support spermiogenesis
4. Secret inhibin
5. Secrete androgen-binding protein

Maintain blood-testis barrier (nurse cell function)

* Preserve luminal/interstitial fluid differences
* Prevent immune cells from attacking sperm

Support spermiogenesis (nurse cell function)

Provide nutrients and stimuli

Secretion of inhibin (nurse cell function)

Negative feedback loop of sperm production

Secrete androgen-bidning protein (nurse cell function)

Stimulates spermiogenesis

Negative feedback loop

Product of a reaction leads to a decrease in that reaction

Positive feedback loop

Product of a reaction leads to a increase in that reaction

Capacitation

Maturation of sperm gaining the ability to penetrate an egg and have greater mobility

Sperm maturation

* Undergo capacitation to become fully functional
* Begin to beat flagella when mixed with seminal gland secretions
* Become capable of fertilization in vaginal tract

Head of sperm

Contains nucleus with chromosomes

Acrosome

Membranous compartment of sperm containing essential fertilization enzymes

Sperm neck

* Attaches head to middle piece


* Contains mitochondria providing ATP to move tail

Sperm tail

Only flagellum in the human body

Sperm anatomy

* Lacks many organs (reduces size and mass)
* Absorbs nutrients (fructose) from surrounding fluid

Pituitary gland releases

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) in response to gonadotropin releasing hormone (GnRH)

LH in men

Promotes release of testosterone

GnRH

* Synthesized in hypothalamus
* Released every 60-90 minutes
* Controlled by negative feedback loops (lots of testosterone inhibits GnRH release)