Reproductive System

Primary Sex Organs (gonads)

Testes in males, ovaries in females

Functions of reproductive system

Produces specialized sex cells (gametes), brings gametes together through sexual intercourse, combines genetic information via fertilization, and supports fetal development and childbirth.

Andro

Men

Epidydymo

Epididymis

Orcho

Testes

Prostato

Prostate gland

Scroto

Scroto

Semino

Semen

Spermo

Sperm

Sex Hormones

Androgens for males, estrogen and progesterone for females. Play roles in the development and function of reproductive organs

Secondary Sexual characteristics

Both sexes; pubic and axillary hair and their associated scent glands, and the pitch of voice.

Reproduction

Union of male and female gametes to form a zygote. Biparental; offspring not genetically identical to either one.

Sexual Differentiation

The process by which an individual develops male or female characteristics. Genetic → Gonadal → phenotypical.

Genetic sex

Gametes: 23 pairs of chromosomes → 22 pairs of autosomes, 1 pair of sex chromosomes. Sex of child determined by type of sperm.

Meiosis

Unique kind of nuclear division that occurs only in gonads. Sexual reproduction cannot take place without meiosis, half and half between both parents.

Haploid

Half the number of chromosomes

Diploid

Total number of chromosomes.

Gonadal Sex

Gonads begin to develop at 5 or 6 weeks. SRY gene (sex-determining region of Y chromosome).

Leydig Cells

Secrete testosterone (male sex hormone).

Sertoli Cells

Protect germ cells, and promote their development. Responsible for nutrients, waste removal, growth factors, etc.

Dihydrotestosterone (DHT)

A male sex hormone made from testosterone that plays a key role in developing male external genitalia.

SRY Gene

Produces SRY protein, which triggers the synthesis of testosterone in an embryo, initiating male sexual differentiation.

Wolffian Ducts

Develop into the male

Mullerian ducts

Develop into the female.

Puberty

Period of life when reproductive organs grow to adult size and become functional. Hypothalamus becomes less sensitive to inhibition by sex hormones.

Function of Male Reproductive System

Production of sperm (spermatogenesis), delivery of sperm to female.

Male Reproductive Organs

Testes and scrotum, male reproductive tract, accessory glands, and penis.

Testes

Produce sperm and lie within the scrotum. Develop in abdominal cavity and then descend into the scrotum between 7-9 months of fetal life. Surrounded by 2 tunics: tunica vaginalis and tunica albuginea.

Cryptorchidism

~3% of male births in which one or both testes fail to descend into the scrotum before birth. Lead to sterility or testicular cancer.

Scrotum

Sac of skin that keeps the testes 3°C lower than core body temperature (needed for sperm production) by dartos and cremaster muscles.

Dartos

Smooth muscle that wrinkles scrotal skin.

Cremaster

Bands of skeletal muscle that elevate the testes.

Penis

A copulatory organ designed to deliver sperm into the female reproductive tract.

Foreskin (prepuce)

Cuff of skin covering the distal end of the penis.

Circumcision

Surgical removal of the foreskin after birth.

Internal Penis

The urethra and three cylindrical bodies of erectile tissie.

Erectile Tissue

Spongy network of connective tissue and smooth muscle riddled with vascular spaces (corpus cavernosum).

Erection

Corpus cavernosum fills with blood causing the penis to enlarge and become rigid.

Corpus spongiosum

Surrounds the urethra and expands to form the glans and bulb of the penis.

Male Reproductive Tract

Sperm are delivered to the exterior through a system. Epididymis → Vas deferens → ejaculatory duct → urethra.

Epididymis

Has cilia that absorbs fluid, nourishes and matures sperm, and moves them via peristalsis; unused sperm break down and are reabsorbed.

Vas Deferens and Ejaculatory Duct

Transports and stores sperm, carrying them from the epididymis to the urethra. Runs from teh epididymis through the inguinal canal into the pelvic cavity.

Vasectomy

Cutting and ligating the vas deferens, which is a nearly 100% effective form of birth control.

Urethra

Conveys both urine and semen. 3 regions: prostatic, membranous, spongy (or penile).

Prostatic Region

Portion surrounded by the prostate

Membranous

Lies in the urogenital diaphragm.

Spongy (or penile)

Runs through the penis and opens to the outside at the external urethral orifice.

Accessory Glands

Empty their secretions into the ducts during ejaculation. Include seminal vesicles, prostate gland, and bulbourethral glands.

Seminal Vesicles

Secrete 60-70% of the volume of semen. Sperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra during ejaculation.

Prostate gland

Secretes a thin, milk, alkaline fluid → accounts for 1/3 of the semen volume. Plays a role in the activation of sperm.

Bulbourethral glands (Cowper’s Glands)

Small glands below the prostate that secrete alkaline mucus to neutralize acidic urine in the urethra before ejaculation.

Semen

A milky fluid of sperm and gland secretions that nourishes, protects, and transports sperm. Clotting factors coagulate semen immediately after ejaculation, fibrinolysin liquefies the sticky mass.

Prostaglands in semen

Reduce cervical mucus thickness and stimulate uterine contractions to help sperm move through the female reproductive tract.

Relaxin

Contained in semen, enhances sperm motility.

Seminalplasmin

In semen, antibiotic protein.

Human Sexual Response

Four phases: Excitation, plateau, orgasm, and resolution.

Excitation

Characterized by increased muscle tone, vasocongestion of sexual organs; also called arousal.

Plateau

Continue vasocongestion.

Orgasm

Contraction of the uterus/vagina and male ejaculatory organs. Dopamine and oxytocin are released.

Resolution

Body returns to pre-excitation condition. Men experience a refractory period.

Erection

A parasympathetic reflex causing the penis to enlarge and stiffen as nitric oxide increases blood flow into erectile tissue; venous compression maintains the erection, and it can be triggered by physical or psychological stimuli.

Ejaculation

A sympathetic reflex that propels semen through the ducts and out the urethra as reproductive organs contract and the bladder sphincter closes.

Refractory period

Period after resolution. Usually impossible for a male to attain another erection or orgasm. May last from 10 min to a few hours.

Sperm

Consists of a head (DNA and acrosome for egg penetration), a midpiece (mitochondria for energy), and a tail (flagellum for movement).

Brain-testicular axis

The hormonal system in which the hypothalamus, anterior pituitary, and testes regulate spermatogenesis and testosterone production.

Male Secondary Sex Characteristics

Increased hair and chest growth, deeper voice, skin thickens, bones grow and increase in density, skeletal muscles increase in size and mass.