Reproductive System (Male) - Lecture Notes

Components in Male Systems:

• Gonads: Testes

• Gametes: Sperm

• Sex Hormones: Testosterone

• Accessory Reproductive Organs: Ducts, glands, and external genitalia

Male reproductive

• Testes are the primary reproductive organ for males

• Accessory:

  • Ducts and tubules leading from testes to penis

  • Male accessory glands

  • Penis

Scrotum Characteristics

• Provides cooler environment

  • Needed for sperm development and maturation

• Ridge seam at midline - raphe

  • Marks location of fusion of two embryonic tissue

• Scrotum wall

  • Thin layer of superficial fascia internal to skin

  • Layer of smooth muscle, dartos muscle, internal to fascia

Scrotum Characteristics: Spermatic Cord

• Multilayered structure traveling from abdomen to testis

• Blood vessels and nerves supplying each testis

• Originates in inguinal canal

  • Tube like passageway through inferior abdominal wall

• Spermatic cord wall consists of three layers

Spermatic Cord Layers

• External spermatic fascia: Formed from aponeurosis of external oblique

• Cremaster muscle and cremasteric fascia: Formed from extensions of internal oblique and its aponeurosis

• Internal spermatic fascia: Formed from fascia deep to abdominal muscles

Scrotum Characteristics (continue)

• Testicular artery:

  • Branch from abdominal aorta

  • Resides within spermatic cord

• Pampiniform plexus:

  • Plexus of veins surrounding testicular artery

  • Pre-cools arterial blood prior to reaching testes

Scrotum response to temperature changes

• With hot temperature

  • Relaxation of dartos muscle

  • Testes move inferior (away from body), cools testes

  • Cremaster muscles relaxes to allow testes to move inferiorly

• With cold temperature

  • Contraction of dartos and cremaster muscles

  • Testes and scrotum pulled closer to body

  • Helps conserve heat

Testes

• Small organs housed within the scrotum

• Produce sperm and androgens

• Covered anteriorly and laterally by a serous membrane

  • Tunica vaginalis

  • Derived from abdominal peritoneum

  • Outer parietal layer and inner visceral layer

  • Separated by cavity filled with serous fluid

Testes: Tunica albuginea

• Thick fibrous capsule covering the testis

• Deep to visceral layer of tunica vaginalis

Testes: Mediastinum testis

• Thickening of tunica albuginea projecting into interior testis

• Blood vessels, ducts, lymph vessels, nerves enter or leave through here

Testes: Septa

• Internal projections of tunica albuginea

• Subdivide internal space into 250 lobules

Testes: Seminiferous tubules

• Extremely convoluted and elongated; up to 4 per lobule

• Nondividing support cells, sustentacular cells

  • Nourish developing sperm

  • Release hormone inhibin when sperm count high

  • Inhibits FSH secretion and regulates sperm production

• Contain dividing germ cells continuously producing sperm

Testes: Blood-testis barrier

• Protects developing sperm from material in blood

• Protects sperm from body’s leukocytes

• Formed from tight junctions between sustentacular cells

Testes: Interstitial spaces and cells

Interstitial spaces:

• Spaces surrounding seminiferous tubules

Interstitial cells:

• Reside in interstitial spaces

• Stimulated to produce androgens by luteinizing hormone

• Most common androgen: testosterone

• Majority released from interstitial cells; small amounts secreted by adrenal cortex

Hormonal regulation

1. Hypothalamus secretes GnRH

2. FSH and LH stimulate spermatogenesis and androgen production

3. Increased testosterone has multiple effects

4. Sustentacular cells release inhibin

5. Testosterone stimulates libido and development of secondary sex characteristics

Spermatogensis

1. Spermatogonia: Stem cells

2. Primary Spermatocyte: Undergoes meiosis I

3. Secondary Spermatocyte: Undergoes meiosis II

4. Spermatids: Mature into sperm

Occurs in the seminiferous tubule

Spermatogonia

• Primordial germ cells from which all sperm develop

• Diploid cells near base of seminiferous tubule

• Surrounded by cytoplasm of sustentacular cell

• Divide by mitosis into new spermatogonium and primary spermatocyte

Clinical View: Sexually Transmitted Infections

• Groups of infectious diseases transmitted via sexual contact

• STIs transmitted because symptoms go unnoticed

• Condoms help prevent spread but not 100% effective

• A  leading cause of pelvic inflammatory disease in women

  • Can lead to blockage of tubes and infertility

Clinical View: Chlamydial

• Most frequently reported in U.S.

• Due to Chlamydial trachomatis bacterium

• Most people are asymptomatic

• May have symptoms of vaginal discharge, painful urination, back pain

• Treated with antibiotics

Clinical View: Genital Herpes

• Caused by herpes simplex virus

• Cyclic outbreaks of blister formation in genital and anal regions

• No cure; antiviral medications lessen severity and length

Clinical View: Gonorrhea

• Caused by bacterium Neisseria gonorrhoeae

• Spread by sexual contract or from mother to baby during delivery

• Treatment with antibiotics; untreated may cause epididymitis in males

Clinical View: Syphilis

• Cause by bacterium Treponema pallidum

• Spread sexually via contact with syphilitic sore, chancre, or in utero

• Treatment with antibiotics

Clinical View: Paternal Age Risks for Disorders in the Offspring

• Males over 45 years of age

• 4 times more likely to pass on genetic mutation than men in their 20s

• Risk increases with age

  • Bipolar disorder, schizophrenia, autism, depression, attention deficient hyperactivity disorder

• Maternal age not correlated with an increase in these disorders

• Age of both sexes carries risk of development problems

Duct System: Epididymis

• Head on superior testis surface

• Body and tall on posterior surface of testis

• Internally contains long duct of the epididymis

  • Lined with pseudostratified columnar epithelium with stereocilia

• Stores sperm until they are fully mature and motile

Duct System: Ductus deferens (vas deferens)

• Sperm enter after leaving epididymis

• Thick-walled muscular tube in the male reproductive system

• Transports sperm from the epididymis to the ejaculatory duct

• Enlarges and forms ampulla

  • Unites with proximal seminal vesicle to form ejaculatory duct

Duct System: Ejaculatory Duct

• Each duct is between 1 and 2 cm long

• Epithelium of pseudostratified ciliated columnar epithelium

• Conducts sperm and a component of seminal fluid toward urethra

• Opens into prostatic urethra

Duct System: Urethra

• Transports semen from ejaculatory ducts to outside of body

• 3 components

  • Prostatic urethra: extending from bladder through prostate gland

  • Membranous urethra: continuing through urogenital diaphragm

  • Spongy urethra: extending through penis

Duct System

Epididymis → Ductus Deferens → Ejaculatory Duct → Urethra

Accessory Glands

• Seminal Vesicles: Fructose for sperm energy

• Prostate Gland: Produces PSA

• Bulbourethral Glands: Lubrication

• Semen: Sperm + seminal fluid

Clinical View: Benign Prostatic Hyperplasia

• Noncancerous enlargement of prostate gland

• Common in older men

• Due to hormonal changes in aging males

• Large nodules forming within prostate and compressing urethra

• Frequent urinating at night, frequent and painful urination

• Can be treated with drugs

  • May require surgical removal of prostatic enlargement

Clinical View: Prostate Cancer

• One of most common malignancies in men over 50

• Forms hard, solid nodules with prostate

• Asymptomatic early on, later urinary symptoms

• Screening with digital rectal exam, PSA test

• Treatment: radiation therapy or surgical removal

Penis

Forms external genitalia with scrotum

Penis: Root

• Internally attached portion of penis

• Dilated internal to body surface

• Forms bulb and crus of penis

• Bulb attaching penis to bulbospongiosus muscle

• Crus attaching penis to public arch

Penis: Body, Glans & Prepuce

• Body: Elongated movable portion

• Glans:

  • Tip of penis

  • Contains external urethral orifice

• Prepuce (foreskin):

  • Circular fold of skin

  • Skin attached to raised edge of the glans

Penis: 3 Cylindrical Erectile Bodies

• Unsheathed by tunica albuginea

• Provides attachment to skin over penile shaft

Paired corpora cavernosa

• Located dorsolaterally & terminate in shaft of penis

Corpus spongiosum

• Ventral to corpora cavernosa in midline

• Contains spongy urethra and continues within the glans

Anatomy of Penis: Cross Section

Phase of male sexual response: Excitement phase

• Erectile bodies of penis composed of venous spaces surrounding artery - blood fills it

• Erectile body becomes rigid - erection

• Parasympathetic control (nitric oxide release)

• Blood unable to leave erectile bodies until excitement over

• Near the end of the phase, heart rate, blood pressure, and respiratory rate increase

Phase of male sexual response: Orgasm

• Intense pleasure, tension release, expulsion of semen

• Ductus deferens move sperm toward urethra

• Accessory glands secrete seminal fluid components:

  • Combine with sperm to form semen

• Internal urethral sphincter of bladder contracted

  • Ensures no urine enter urethra

• Ejaculation at end of orgasm:

  • Occurs due to sympathetic control

Sex Differentiation: Genetic Sex

• Genotypic sex based on sex chromosomes inherited

• Determined at fertilization

• XX → genetic female

• XY → genetic male

Sex Differentiation: Phenotypic Sex

• Refers to at he appearance of the individual’s internal and external genitalia

• Ovaries and female external genitalia, phenotypic female

• Testes and male external genitalia, phenotypic male

• Apparent seventh week of development

Sex-determining region Y (SRY) gene

• Located within larger testis-determining factor (TDF) region on Y chromosome

• In genetic male with Y chromosome

  • SRY gene expressed

  • Produces proteins to stimulate androgens

  • Androgens initiate male phenotypic development

• If Y chromosome is absent, or lacks or has an abnormal SRY gene, female phenotypic sex results

Duct and gonad development: Genital Ridges

• Form in fifth week of embryonic development

• Form from intermediate mesoderm

• Will form gonads

• Medial to developing kidneys

Duct and gonad development: Primordial germ cells

• Migrate from yolk sac to genital ridges between weeks 5 and 6

• Will form future gametes

Duct and gonad development: Mesonephric ducts

• Form most of male duct system

• Connect mesonephros to developing urinary bladder

Duct and gonad development: Paramesonephric ducts

• Form most of female duct system

• Include uterine tubes, uterus, superior vagina

• Appear lateral to mesonephric ducts

Duct and gonad development

• Only one remaining in fetus

Female:

• Development of paramesonephric ducts

• Degeneration of mesonephric ducts

Male:

• Development of mesonephric ducts

• Degeneration of paramesonephric ducts

Puberty

• Increased GnRH, FSH, LH secretion

• Females: Breast development, menarche

• Males: Testicular and penile growth, voice deepens

Clinical View: Intersex Conditions (Disorders of Sex Development)¹

• Discrepancy between genotype and external genitalia

• True gonadal intersex - very rare

  • Individual with both ovarian and testicular structures

  • Ambiguous external genitalia

  • Genetic male or genetic female

• Pseudohermaphroditism

  • Genetic sex and phenotypic sex do not match

Clinical View: Intersex Conditions (Disorders of Sex Development)²

46 XY intersex:

• Genetic male with external genitalia resembling a female

• From reduction of lack of male hormones during development

46 XX intersex

• Genetic female with external genitalia resembling male

• Clitoris enlarged and labia partially fused

• May result if fetus exposed to excessive androgens

• May result from congenital adrenal hyperplasia

  • Fetus’s adrenal glands producing excessive androgens

The areolar glands are ___

sebaceous glands

What do testes produce

• androgens

• spermatozoa

A serous membrane, the tunica ___around each testis has a parietal and visceral layer

vaginalis

The labia majora of the female are homologous to the ___ of the male

scrotum

Name of the process where spermatids become mature spermatozoa

spermiogensis

All the stages in which the cells are haploid

• spermatozoon

• secondary spermatocyte

• spermatid