What is Reproduction? In simple terms, reproduction is the process by which organisms create descendants. In human reproduction, two kinds of sex

What is Reproduction?What is Reproduction?

In simple terms, reproduction is the process by which organisms create descendants.

In human reproduction, two kinds of sex cells or gametes are involved--- the sperm (male gamete) and egg (female gamete).

Reproductive SystemReproductive System

The reproductive system is a system of organs within an organism which work together for the purpose of reproduction.

Male Reproductive Male Reproductive System System

The human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproductive process.

Figure 28.1

Male Reproductive Male Reproductive System Gross AnatomySystem Gross Anatomy

Gonad - the organ that makes gametes

Testes – male gonad Function – production of testosterone which

stimulates the production of sperm as well as give secondary sex characteristics beginning at puberty.


External Features of Testes

- Testes is covered with Scrotum

* Scrotum

– a protuberance of skin and muscle which contains the testicles, and keeps them at a temperature slightly lower than that of the rest of the body.

- higher temperatures may be damaging to sperm count.



* Scrotum - has two muscles that regulate the temperature of the testes:

Dartos Muscle

- a layer of smooth muscle fibers in the subcutaneous tissue of the scrotum (surrounding the scrotum).

- responsible for wrinkling up the scrotum, in conditions of cold weather, in order to maintain the correct temperature for spermatogenisis



* Scrotum - has two muscles that regulate the temperature of the testes:

Cremaster Muscle

- a thin strand of skeletal muscle associated with the testes and spermatic cord.

- a continuation of the internal oblique muscle of the abdominal wall, from which it is derived




Internal Structure of Testes

Seminiferous tubules

- each testis contains over 100 yards of tightly packed seminiferous tubules. (90% of the weight of testis)

- specific location of meiosis.

- In between the seminiferous tubules are instititial cells, or, Cells of Leydig. They are responsible for secreting the male sex hormones



Seminiferous tubules

- The epithelium of the tubule consists of Sertoli cells, which are tall, columnar type cells that line the tubule

- main function of Setori cells is to nurture the developing sperm cells through the stages of spermatogenesis.

- In between the Sertoli cells are spermatogenic cells.



Efferent ductules

- The sperm are transported out of the testis and into the epididymis through a series of efferent ductules..




Blood Supply of Testes

- The testes receive blood through the testicular arteries (gonadal artery). Venous blood is drained by the testicular veins. The right testicular vein drains directly into the inferior vena cava. The left testicular vein drains into the left renal vein.


Epididymis

- The seminiferous tubules join together to become the epididymis.

- a tube that is about 20 feet long that is coiled on the posterior surface of each testis

- where the sperm complete their maturation and their flagella become functional

- also a site to store sperm until the next ejaculation

- Smooth muscle in the wall of the epididymis propels the sperm into the ductus (vas) deferens.


Epididymis

3 regions:

The head (Caput). The head of the epididymis receives spermatozoa via the efferent ducts of the mediastinum of the testis. It is characterized histologically by a thin myoepithelium. The concentration of the sperm here is dilute.

The body (Corpus)

The tail (Cauda). This has a thicker myoepithelium than the head region, as it is involved in absorbing fluid to make the sperm more concentrated.


Epididymis

Pathology:

Epididymitis – inflammation of the epididymis

Epididymectomy – surgical removal of the epididymis under local anesthesia




Vas deferens (ductus deferens)

- also called sperm duct, or, spermatic deferens

- they transport sperm from the epididymis in anticipation of ejaculation.

- There are two such ducts, connecting the left and right epididymis to the ejaculatory ducts in order to move sperm.

- Each tube is about 30 centimeters long and is muscular just like the penis


Vas deferens (ductus deferens) : Function in Ejaculation

- undergoes Peristalsis: during ejaculation the smooth muscle in the walls of the ductus deferens or vas deferens contracts reflexively, thus propelling the sperm forward.

- The sperm is transferred from the vas deferens into the urethra, collecting secretions from the male accessory sex glands which form the bulk of semen.


Vas deferens (ductus deferens) : Blood Supply

- The vas deferens is supplied by an accompanying artery (artery of vas deferens). This artery normally arises from the inferior vesical artery, a branch of the internal iliac artery.


Vas deferens (ductus deferens) : Vasectomy

Vasectomy

- a method of contraception in which the vasa deferentia are permanently cut

- also known as deferentectomy

Figure 28.3

Male Reproductive Male Reproductive System System Gross AnatomyGross Anatomy

Ejaculatory duct

- formed by the union of the vas deferens with the duct of the seminal vesicle.

- 2cm in length

- During ejaculation, semen passes through the ducts and exits the body via the penis.


Vasectomy


Accessory Glands Seminal Vesicles

- secrete a significant proportion of the fluid that ultimately

becomes semen. Prostate

- stores and secretes a slightly alkaline (pH 7.29) fluid, milky or white in appearance, that usually constitutes 25-30% of the volume of the semen along with spermatozoa and seminal vesicle fluid.


Accessory Glands Bulbourethral glands

- each gland produces a clear, viscous secretion known as pre-ejaculate during sexual arousal.

- This fluid helps to lubricate the urethra for spermatozoa to pass through, it neutralizes traces of acidic urine in urethra, and helps flush out any residual urine or foreign matter




Penis

- external male genital organ

- male organ of urination.

- the distal end is called the glans penis and is covered with a fold of skin called the prepuce or foreskin


Penis

3 Main Parts: Shaft – “body” Glans - sensitive bulbous structure at the distal end Prepuce – “fore skin”

Tissues Corpora cavernosa – sponge-like regions of erectile

tissue which contain most of the blood in the penis during penile erection.

(two facing each other at dorsal side) Corpus spongiosum - mass of spongy tissue

surrounding the male urethra (one in between cavernosa on the ventral side)


Male Urethra

Urethra - a tube which connects the urinary bladder to the outside of the body.

- has an excretory function in to pass urine to the outside

- passageway of semen (males)

- the urethra is about 8 inches (20 cm) long and opens at the end of the penis. (males)


Male Urethra

4 Parts:

1. pre-prostatic urethra

- the intramural part of the urethra and varies between 0.5 and 1.5 cm in length depending the fullness of the bladder.

- epithelium: transitional


Male Urethra

2. prostatic urethra

- Crosses through the prostate gland.

- epithelium: transitional

openings (verumontanum):

(1) ejaculatory duct - receives sperm from the vas deferens and ejaculate fluid from the seminal vesicle

(2) prostatic ducts - where fluid from the prostate enters and contributes to the ejaculate

(3) prostatic utricle - which is merely an indentation.


Male Urethra

3. membranous urethra

- A small (1 or 2 cm) portion passing through the external urethral sphincter.

- narrowest part of the urethra.

- located in the deep perineal pouch.

- The ducts of the bulbourethral glands (Cowper's gland) enter here.

- epithelium: Pseudostratified columnar


Male Urethra

4. spongy urethra (or penile urethra)

- Runs along the length of the penis on its ventral (underneath) surface.

- about 15–16 cm in length, and travels through the corpus spongiosum.

- The ducts from the urethral gland (gland of Littre) enter here.

- epithelium: pseudostratified columnar (proximally)

stratified squamous (distally)


Male Urethra


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What is Reproduction? In simple terms, reproduction is the process by which organisms create descendants. In human reproduction, two kinds of sex