PAN 201 Male Reproductive System Adolescence Puberty Burst

PAN 201 Male Reproductive System

Adolescence • Puberty • Burst of hormones activate maturation of the gonads: testes • Begins: 9 – 14 yrs of age • Abnormally early = precocious puberty • Delayed = eunuchoidism

General Physical Changes • Enlargement of the external and internal genitalia • Voice changes • Hair growth • Mental changes • Changes in body conformation and skin • Sebaceous gland secretions thicken/increase acne

Similarities and differences between males and females, but same goal: new life • Primary sex organs: gonads • Testes in males • Ovaries in females – These produce the gametes (sex cells) • Sperm in males • Ovum (egg) in females – Endocrine function also: secretion of hormones • Accessory sex organs – Internal glands and ducts – External genitalia 4

Male reproductive system • Testes (singular testis) or testicles: the gonads – In embryo, first develop in posterior abdominal wall, then migrate – Internal body temp too hot for viable sperm – Temp cooler in the scrotum because of superficial position 5

Testes • Each testis is an oval structure about 5 cm long and 3 cm in diameter • Covered by: tunica albuginea • Located in the scrotum • There about 250 lobules in each testis. Each contains 1 to 4 -seminiferous tubules that converge to form a single straight tubule, which leads into the rete testis. • Short efferent ducts exit the testes. • Interstitial cells (cells of Leydig), which produce male sex hormones, are located between the seminiferous tubules within a lobule.

scrotum • consists of skin and subcutaneous tissue • A vertical septum, of subcutaneous tissue in the center divides it into two parts, each containing one testis. • Smooth muscle fibers, called the dartos muscle, in the subcutaneous tissue contract to give the scrotum its wrinkled appearance. When these fibers are relaxed, the scrotum is smooth. • the cremaster muscle, consists of skeletal muscle fibers and controls the position of the scrotum and testes. When it is cold or a man is sexually aroused, this muscle contracts to pull the testes closer to the body for warmth.

• • Scrotum (=pouch) has septum dividing it Each testis is about 2. 5 cm x 4 cm in size, within scrotum Dartos and cremaster muscles move testes in response to hot or cold Serous sac partially encloses each testis: the tunica vaginalis* – Develops as outpocketing of peritoneal cavity • Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule – Septal extensions of it divide testis into 250 -300 lobules – Each lobule contains 1 -4 coiled seminiferous tubules: make sperm * * 11

• Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule – Septal extensions of it divide testis into 250 -300 lobules* • Each lobule contains 1 -4 coiled seminiferous tubules*: make sperm – Converge to form straight tube (tubulus rectus), then conveys sperm into rete testis • • Sperm leave testis through efferent ductules which enter epididymis* Blood supply: pampiniform plexus: from L 2 not pelvic level, since descended from abdomen Pampiniform plexus epididymis * * * * (lateral views) * Epididymis is commashaped 12

Duct System • Sperm cells pass through a series of ducts to reach the outside of the body. After they leave the testes, the sperm passes through the epididymis, ductus deferens, ejaculatory duct, and urethra.

Epididymis • a long tube (about 6 meters) located along the superior and posterior margins of the testes. • Sperm that leave the testes are immature and incapable of fertilizing ova. They complete their maturation process and become fertile as they move through the epididymis. Mature sperm are stored in the lower portion, or tail, of the epididymis

• Sperm are ejaculated from the epididymus – Not directly from the testes • Vas deferens* (or ductus deferens) 45 cm (18”) – Stores and transports sperm during ejaculation – Runs superiorly from scrotum within spermatic cord, through inguinal canal and enters pelvis • Vas* arches – Histo: see previous slide * medially over ureter • Descends along posterior wall of bladder • Ends in ampulla which joins duct of seminal vesicle to form short ejaculatory duct • Each ejaculatory duct runs within prostate where empties into prostatic urethra 15

spermatic cord • contains the proximal ductus deferens, testicular artery and veins, lymph vessels, testicular nerve, cremaster muscle and a connective tissue covering.

Ductus Deferens [vas deferens] • a fibromuscular tube that is continuous with the epididymis. • enters the abdominopelvic cavity through the inguinal canal and passes along the lateral pelvic wall, behind bladder & toward the prostate gland. Just before it reaches the prostate gland, each ductus deferens enlarges to form an ampulla. • Sperm are stored in the proximal portion of the ductus deferens, near the epididymis

Ejaculatory Duct • Each ductus deferens, at the ampulla, joins the duct from the adjacent seminal vesicle (one of the accessory glands) to form a short ejaculatory duct. • Each ejaculatory duct passes through the prostate gland empties into the urethra.

Urethra • extends from the urinary bladder to the external urethral orifice at the tip of the penis. • It is a passageway for sperm and fluids from the reproductive system and urine from the urinary system. • divided into three regions: The prostatic urethra, the membranous urethra & the penile urethra (also called spongy urethra or cavernous urethra)

Inguinal hernia Spermatic cord: • Vas deference is the largest component • Is a tube of fascia also containing nerves and vessels • Runs in inguinal canal Inguinal canal has 2 rings: 1. Superficial (medial) 2. Deep 20

accessory glands • are the seminal vesicles, prostate gland, and the bulbourethral glands. These glands secrete fluids that enter the urethra.

Posterior view Lateral view • Seminal vesicles – On posterior bladder – Secrete fluids and substances which constitute 60% of semen – Their ducts join vas deferens • Sperm and seminal fluid mix in ejaculatory duct • Prostate: note here and next slide • Bulbourethral glands – Secrete mucus during sexual excitement and ejaculation (lubricant) 22

Prostate • a firm, dense structure about the size of a walnut that is located just inferior to the urinary bladder. • encircles the urethra as it leaves the urinary bladder. • Numerous short ducts from the prostate gland empty into the prostatic urethra. The secretions of the prostate are thin, milky colored, and alkaline. They function to enhance the motility of the sperm.

The Prostate • Size & shape of a chestnut • Encircles 1 st part of urethra • 3 types of glands – Contribute to semen (milky fluid and enzymes) – PSA measured as indicator of prostate cancer (“prostate specific antigen”) • Fibromuscular stroma 24

Posterior view • Male external genitalia – Scrotum – Penis • Penis: 3 parts – Root (attached) – Free shaft or body – Enlarged tip called glans penis • Skin of penis is loose – Prepuce or foreskin • Cuff around glans • Removed if circumcision • See cross section, penis – Urethra (called spongy or penile urethra here) – 3 erectile bodies (parasympathetic stimulation during sexual excitation causes engorgement with blood allowing erection): • Corpus spongiosum • Pair of corpora cavernosa – Vessels and nerves • Ejaculation caused by sympathetic nerves – Contraction of smooth muscle of ducts and penis 25

Review pics 26

Bulbourethral Glands (Cowper's) • small, about the size of a pea, and located near the base of the penis. A short duct from each enters the proximal end of the penile urethra. • In response to sexual stimulation, the bulbourethral glands secrete an alkaline mucus-like fluid

Seminal Vesicles • glands posterior to the urinary bladder. • Each has a short duct that joins with the ductus deferens at the ampulla to form an ejaculatory duct, which then empties into the urethra. • The fluid is viscous and contains fructose, prostaglandins and proteins.

Posterior view Lateral view • Seminal vesicles – On posterior bladder – Secrete fluids and substances which constitute 60% of semen – Their ducts join vas deferens • Sperm and seminal fluid mix in ejaculatory duct • Prostate: note here and next slide • Bulbourethral glands – Secrete mucus during sexual excitement and ejaculation (lubricant) 29

penis • is a cylindrical pendant organ located anterior to the scrotum and functions to transfer sperm to the vagina. • consists of three columns of erectile tissue that are wrapped in connective tissue and covered with skin. The two dorsal columns are the corpora cavernosa. The single, midline ventral column surrounds the urethra and is called the corpus spongiosum.

penis 3 parts: a root, body (shaft), and glans penis. The root of the penis attaches it to the pubic arch the body is the visible, pendant portion. The corpus spongiosum expands at the distal end to form the glans penis. • The urethra, which extends throughout the length of the corpus spongiosum, opens through the external urethral orifice at the tip of the glans penis. A loose fold of skin, called the prepuce, or foreskin, covers the glans penis. • •

Erection • Involves increase in length, width & firmness • Changes in blood supply: arterioles dilate, veins constrict • The spongy erectile tissue fills with blood

Hormones q. Follicle-stimulating hormone (FSH) stimulates spermatogenesis • Interstitial Cell Stimulating Hormone (ICSH) stimulates the production of testosterone • testosterone stimulates the development of male secondary sex characteristics & spermatogenesis.

Spermatogenesis • Sperm are produced within the seminiferous tubules. • Interspersed within the tubules are large cells which are the sustentacular cells (Sertoli's cells), which support and nourish the other cells.

Spermatogenesis • Early in embryonic development, primordial germ cells enter the testes and differentiate into spermatogonia • Spermatogonia are diploid cells, each with 46 chromosomes (23 pairs) located around the periphery of the seminiferous tubules. • At puberty, hormones stimulate these cells to begin dividing by mitosis. Some remain at the periphery as spermatogonia. • Others become primary spermatocytes. Because they are produced by mitosis, primary spermatocytes, like spermatogonia, are diploid and have 46 chromosomes.

Spermatogenesis • Each primary spermatocytes goes through the first meiotic division, meiosis I, to produce two secondary spermatocytes, each with 23 chromosomes (haploid). Just prior to this division, the genetic material is replicated • During meiosis I, one chromosome, goes to each secondary spermatocyte. In the second meiotic division, meiosis II, each secondary spermatocyte divides to produce two spermatids. There is no replication of genetic material in this division, but a single-stranded chromatid goes to each cell. • As a result of the two meiotic divisions, each primary spermatocyte produces four spermatids. • each spermatid has 23 chromosomes (haploid), one from each pair in the original primary spermatocyte.

Spermatogenesis • The final step in the development the spermatids formed from spermatogenesis become mature spermatozoa, or sperm. • The mature sperm cell has a head, midpiece, and tail. The head, also called the nuclear region, contains the 23 chromosomes surrounded by a nuclear membrane. The tip of the head is covered by an acrosome, which contains enzymes that help the sperm penetrate the female gamete. The midpiece, metabolic region, contains mitochondria that provide adenosine triphosphate (ATP). The tail, locomotor region, uses a typical flagellum for locomotion.

Spermatogenesis: sperm formation • • Cross section of seminiferous tubule Begins at puberty 400 million sperm/day For baby not to end up with twice as many chromosomes as the parents, the sperm (as well as the egg) needs to have only half (1 n) the # of chromosomes (1 of each of the 23) (2 n means 2 of each chromosome, one from each parent, totaling 23 pairs = 46 chromosomes) • Three stages: – Formation of spermatocytes – Meiosis – Spermiogenesis 40

• 1 st stage: formation of spermatocytes Cross section of seminiferous tubule – Spermatogonia are stem cells • Least differentiated (earliest in the process) • Lie in basal lamina – Divide continuously by mitosis (result 2 n or diploid): daughter cells A (remains a stem cell) or B (goes on) – When start to undergo meiosis are by definition called spermatocytes • 2 nd stage: meiosis I – Each primary spermatocytes (2 n) undergoes meiosis I to become 2 secondary spermatocytes: – Each secondary spermatocyte undergoes meiosis II to become 2 spermatids – Therefore 4 total spermatids from each spermatogonium • 3 rd stage: spermiogenesis – Spermatids differentiate into sperm 41

Stage 3: Spermiogenesis: spermatid streamlined to sperm – Head contains • Nucleus with chromatid (genetic material) • Acrosome with enzymes for penetrating egg – Midpiece: mitochondria spiraled around the core of the tail – Tail is an elaborate flagellum (allows sperm to swim) know these parts 42

• Sperm can swim only after they have left the testis • Process of spermatogenesis is controlled by two hormones * – FSH (follicle stimulating hormones) from anterior pituitary – Testosterone • primary male hormone • produces by testes • Sperm surrounded by Sertoli* (sustenacular) cells: tight junctions – – Prevents escape of unique antigens seen as foreign These would activate the immune system Autoimmune response would cause sterility Other functions as well • Interstitial or Leydig cells: secrete androgens – Male sex hormones – Main one is testosterone – Into blood, sustain all male sex characteristic and sex organs 43

• Sperm leave testis though efferent ductules – Lined by simple columnar epithelium – Cilia and smooth muscle in wall help move sperm along • Sperm mature in epididymus (20 days) – Head of epididymus contains the efferent ductules which empty into duct of the epididymus – Sperm gain ability to swim – Sperm can be stored in epididymus for several months (reabsorbs fluid) * Duct of epididymis: highly coiled 6 m long duct (pic left is multiple coils of same duct) *Note pseudostratified columnar epithelium Ductus (vas) deferens: note thick layers of smooth muscle 44

Seminiferous Tubule – cross section Sertoli Cells (nurse cells) Receptors for FSH & testosterone Produce – androgen binding protein - sulfated glycoproteins - transferin - inhibin Junctional complexes Leydig Cells (interstitial cells) Receptors for LH Produce Testosterone Spermatogonia – division by mitosis Spermatocytes – division by meiosis Intercellular bridges

Spermatogenesis • The sperm are released into the lumen of the seminiferous tubule and leave the testes. They then enter the epididymis where they undergo their final maturation and become capable of fertilizing a female gamete. • Sperm production begins at puberty and continues throughout the life of a male. • The entire process, beginning with a primary spermatocyte, takes about 74 days. After ejaculation, the sperm can live for about 48 hours in the female reproductive tract.

Seminal Fluid or Semen • a slightly alkaline mixture of sperm cells and secretions from the accessory glands. • Secretions from the seminal vesicles make up about 60 percent of the volume of the semen, with most of the remainder coming from the prostate gland. The sperm and secretions from the bulbourethral gland contribute only a small volume. • The volume of semen in a single ejaculation may vary from 1. 5 to 6. 0 ml. There are between 50 to 150 million sperm per milliliter of semen. Sperm counts below 10 to 20 million per milliliter usually present fertility problems.

ØCriptochism ØErectile Dysfunction [ED] also known as impotence ØPriapism- prolonged erection at least four hours long, without physical or psychological stimulation.