Male Reproductive system

Male Reproductive system

Male-Reproductive-system

Objectives

At the end of this lecture, student will be able to

• List the organs of male reproductive system

• Describe the structure of male reproductive system

• Describe the process of spermatogenensis

• Explain the negative feedback control on blood levels of testosterone

REPRODUCTIVE SYSTEM

• Reproduction – process by which new individuals of a species are produced and the genetic material is passed from generation to generation

The organs of reproduction are grouped as

• Gonads (produce gametes)

• Ducts (transport and store gametes)

• Accessory sex glands (produce materials that support gametes) and

• Supporting structures (have various roles in reproduction)

Male reproductive system

Sagittal section of male reproductive system

Sagittal-section-of-male-reproductive-system

Anatomy of male reproductive system

Scrotum 

• A sac that hangs from the root of the penis 

• Consists of loose skin and underlying subcutaneous layer

• Supports the testes

• Single pouch of skin separated into lateral portions by a median ridge called the raphe

Scrotal septum divides the scrotum into two sacs, each containing a single testis

Septum – made up of a subcutaneous layer and muscle tissue, the dartos muscle

• Each testis in the scrotum is associated with cremaster muscle, a series of small bands of skeletal muscle

Testes/ Testicles

• Paired oval glands (gonads) in the scrotum

– Seminiferous tubules – sperm cells are made

– Sertoli cells (sustentacular cells)- nourish sperm cells and secrete inhibin

– Leydig (interstitial) cells, produce the male sex hormone testosterone

• Testes descend into the scrotum through the inguinal canals

• Failure of the testes to descend, cryptorchidism

Sertoli cells – secrete androgen-binding protein (ABP) à binds to testosterone àkeeps its concentration high in the seminiferous tubule

– Secrets inhibin à inhibition of FSH helps à regulate the rate of spermatogenesis.

• Testosterone

  Controls the growth, development, and maintenance of sex organs

  Stimulates bone growth, protein anabolism, sperm maturation

  Stimulates development of masculine secondary sex characters

System of ducts

• Ducts of the Testis

– Seminiferous tubules

– Straight tubules

– Rete testis

• Sperm flow out of the testes through the efferent ducts

• Ductus epididymis – site of sperm maturation and storage

• Ductus (vas) deferens

– Stores sperm

– Propels them toward the urethra during ejaculation

• Ejaculatory duct

– Union of the duct from the seminal vesicle and vas deferens

– Passage for ejection of sperm and secretions of the seminal vesicles into the first portion of the urethra, the prostatic urethra

• Urethra in males is subdivided into 3 portions:

– Prostatic

– Membranous

– Spongy (penile) urethra- ends at the external urethral orifice

Sagittal section of a testis showing seminiferous tubules

Sagittal-section-of-a-testis-showing-seminiferous-tubules

Accessory Sex Glands

Includes:

Seminal Vesicles/Seminal glands

– Convoluted pouch like structures

– Posterior to the base of the urinary bladder

– Anterior to the rectum

Secrete alkaline, viscous fluid

– Neutralize acid in the female reproductive tract

– Fructose for ATP production by sperm

– Sperm motility and viability

– Semen coagulate after ejaculation

Prostate gland

• A single, doughnut-shaped gland

• About the size of a golf ball; Inferior to the urinary bladder

• Surrounds the prostatic urethra

• Secretes a milky, slightly acidic fluid (pH 6.5) contains

– Citric acid in prostatic fluid – ATP production via the Krebs cycle

– Proteolytic enzymes – break down the clotting proteins from the seminal vesicles

– Seminal plasmin in prostatic fluid- an antibiotic, destroy bacteria

Bulbourethral Glands

• Paired bulbourethral glands/Cowper’s glands; about the size of peas.

• Inferior to the prostate on either side of the membranous urethra

• Their ducts open into the spongy urethra

• Secrete an alkaline fluid into the urethra

– Protects the passing sperm by neutralizing acids from urine

• Secrete mucus

– Lubricates the end of the penis and the lining of the urethra

– Decreases the no. Of sperm damaged during ejaculation

Penis

• Contains the urethra

• Passageway for the ejaculation of semen and the excretion of urine

• Consists of

– A body

– Glans penis

– A root

Body of the penis, composed of 3 cylindrical masses of tissue, each surrounded by fibrous tissue, tunica albuginea

– Two dorsolateral masses, corpora cavernosa penis

– Smaller midventral mass, the corpus spongiosum penis, contains spongy urethra

Glans penis

• Enlarged acorn-shaped region

• At the distal end of the corpus spongiosum penis

   Its margin is the corona

• Covering the glans in an uncircumcised penis is the loosely fitting prepuce or foreskin

Root of the penis – attached portion

Has – Bulb of the penis

– The expanded portion of the base of the corpus spongiosum crura of the penis

Internal structure of the penis

Internal-structure-of-the-penis

Semen

• Mixture of sperm and seminal fluid

• Consists of the secretions of the seminiferous tubules, seminal vesicles, prostate, and bulbourethral glands

• Provides the fluid in which sperm are transported

• Supplies nutrients

• Neutralizes the acidity of the male urethra and the vagina

Internal structure of the penis

SPERMATOGENESIS

SPERMATOGENESIS

• Process whereby immature spermatogonia develop into sperm

• Occurs in the testes

• Takes 65–75 days

• Sequence includes

– Meiosis I

– Meiosis II

– Spermiogenesis

• Forms 4 haploid sperm (spermatozoa) from each primary spermatocyte

• Mature sperm consist of a head and a tail

• Function – fertilize a secondary oocyte

Hormonal Control of the Testes

• Release of FSH is stimulated by GnRH and inhibited by inhibin

• Release of LH is stimulated by GnRH and inhibited by testosterone.

Hormonal-Control-of-the-Testes

Negative feedback control of blood level of testosterone

Negative-feedback-control-of-blood-level-of-testosterone

Gonadotrophs of the anterior pituitary produce luteinizing hormone (LH).

Summary

• Reproduction is the process by which new individuals of a species are produced and the genetic material is passed from generation to generation

• Reproductive organs – Gonads, Ducts, Accessory sex glands andS upporting structures

• Male structures of reproduction include the testes, ductus epididymis, ductus (vas) deferens, ejaculatory duct, urethra, seminal vesicles, prostate, bulbourethral (Cowper’s) glands, and penis

• Spermatogenesis, occurs in the testes, is the process whereby immature spermatogonia develop into sperm

• Testosterone controls the growth, development, and maintenance of sex organs; stimulates development of masculine secondary sex characteristics

• Levels of testosterone in blood is controlled by negative feedback mechanism

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