Chapter 27 LECTURE

Ovum

• Haploid (23 chromosomes)

• Female gamete

Sperm

• Haploid (23 Chromosomes)

• Male gamete

Zygote

• Diploid (46 Chromosomes)

• Male and female gametes

Embryo

Each cell of child will have 23 chromosomes from each parent

Sexual Reproduction

Produces new individuals

Gonads

Produce gametes & secrete sex hormones

Somatic Cells

• Diploid cells

• 23 pairs of chromosomes

• 22 autosomes & 1 pair of sex chromosomes

Gametes

• Haploid cells

• Single set of chromosomes (23)

• Produced by special type of division: Meiosis

Meiosis

• Sexual reproduction

• Reduce chromosome number by half

• 2 stages

• Diploid- 2n

• Haploid n

Genetic Recombination

• Homologous Chromosomes → Chromosome Crossover → Recombinant Chromatids

• Exchange of genetic material between different organisms or chromosomes, creating new gene combinations that increase genetic diversity

Testes

Male Gonads

Male System of Ducts

Epididymis, ductus deferens, ejaculatory ducts & urethra

Male Accessory Sex Glands

Seminal vesicles, prostate & bulbourethral glands

Male Support Structures

Scrotum & penis

Scrotum

• Support structure for testes

• Sac of loose skin, fascia & smooth muscle divided into 2 pouches by septum

• Raphe

Testes

• Paired, oval glands in the scrotum

• Surrounded by two tunics

• Mediastinum testis (houses rate testis)

• Seminiferous tubules

Two Tunics in Testes

• Tunica albuginea (deep)

• Tunica Vaginalis (superficial)

Seminiferous tubule lobules (1)

Where is sperm made?

Straight Tubule (2)

Where does sperm go after it’s made?

Rete Testis (3)

After the straight tubule, sperm enters…

Efferent Ducts (4)

After the rate testes, sperm enters…

Epididymis (5)

After the efferent ductule, sperm enters…

Ductus Deferens (6)

After sperm leaves the epididymis, it enters…

Hydrocele

• A fluid-filled sac in the scrotum that causes swelling, typically around one or both testicles

• ~10% of newborns have this

Testes

• Develop near kidney & descend through inguinal canals ~7th month of fetal development

Cryptorchidism

a common pediatric condition where one or both testicles fail to descend into the scrotum before birth

Support Cells of the Seminiferous Tubule

• Sertoli (Sustentacular) cells

• Leydig (Interstitial) cells

Sertoli (Sustentacular) Cells “Teacher Cells”

• From blood-testis barrier

• Support, protect & nourish spermatogenic cells

• Produce fluids

• Control release of sperm into lumen

• Secrete Inhibin (when sperm production is high)

Leydig (Interstitial) cells “Power-Up Cells”

• Arise from dividing stem cells

• Produce androgens (Mainly testosterone stimulated by LH)

Spermatogenesis

• Begins at puberty

• Takes ~2.5 months

• Stimulated by FSH & LH

Spermatogenesis Pathway

Spermatogonia (2n) → Primary Spermatocyte (2n) → secondary spermatocyte (n) → spermatids (n) → spermatozoa/sperm (n)

Spermiogenesis

Spermatids → sperm cell

Spermiation

Release of sperm cell from sertoli (sustentacular) cells

Sperm

• Head- 23 Chromosomes

• Midpiece- Mitochondria

• Tail- Flagellum

Head of Sperm

• DNA

• Acrosome (hyaluronidas & proteinase enzymes)

~100-300 million

How many sperm are produced each day?

Five

Once ejaculated, sperm remain viable for up to ___ days within the female reproductive tract

Epididymis

• Sperm learn to swim

• Sperm grow stronger

• Stored until ready

Vas Deferens

Highway that carries sperm from the epididymis to the glands that add fluid

Pathway of sperm

• Seminiferous Tubules

• Straight tubules

• Rete Testis

• Efferent Ducts

• Epididymis

• Ductus Deferens

Spermatic Cord

• Ductus deferens

• Testicular artery

• Veins draining the testes

• Autonomic nerves

• Lymphatic vessels

• Cremaster muscle

Plexus of testicular veins

What are the veins draining the testes called?

• Seminal Vesicles

• Prostate

• Bulbourethral (Cowper’s) Glands

What are the accessory glands of the Male reproductive system?

Seminal Vesicles

• Viscous, whitish-yellow, alkaline fluid

• Fructose, prostaglandins, clotting proteins, seminal plasmin

Prostate

• Slightly milky fluid that is weakly acidic

• Citric acid, proteolytic enzymes

Bulbourethral (Cowper’s) Gland

• Clear, viscous mucin (alkaline)

• Helps clean & protect the pathway

Semen

• Sperm and Seminal fluid

• pH 7.2-7.7

• Coagulates & reliquefies on ejaculation

• An average ejaculate contains 50-150 million sperm/mL

• Analysis

• Motility

• Count

• Shape of sperm

What does a semen analysis consist of?

7.2-7.7

What’s the pH of semen?

Penis

• Forms of external genitalia with scrotum

• Passageway for semen & urine (urethra)

Body of Penis

• Composed of 3 erectile tissue masses filled with blood sinuses

• Corpus Cavernosa

• Corpus Sopongiosum

Root of Penis

• Bulb of penis

• Crus of penis

Tip of Penis

• Corona

• Glans penis

• Prepuce (foreskin)

Erection

• Parasympathetic fibers release & cause local production of NO (nitric oxide) → smooth muscle in arterioles to relax & dilate allowing large amounts of blood to enter penis

• Blood enters penis compressing veins- blood trapped

• Impotence

Impotence

Erectile dysfunction is also known as…

Ejaculation

• Due to sympathetic stimulation

• Muscle contractions close sphincter at base of bladder

• Move fluids through ductus deferent, seminal vesicles, & ejaculatory ducts

• Contraction of muscles in ischiocavernosus & bulbospongiosus

Ischiocavernosus & bulbospongiosus

Which muscles contract during ejaculation?

Ovaries

Female gonads

1. Ovarian ligament

2. Suspensory ligament

3. Broad ligament

Which 3 ligaments hold the ovaries in place?

Ovaries consist of:

• Germinal epithelium

• Tunica albuginea

• Ovarian cortex

• Ovarian medulla

Ovarian Cortex

Outer layer where eggs grow

Ovarian Medulla

Middle layer with blood vessels

Atresia

~99% of the follicles in the ovary will undergo ____, which can occur at any stage of folliculogenesis.

Follicles

Contain oocytes in various stages of development, and their supporting cells (follicular cells/granulosa cells)

6 Main types of Follicles

• Primordial follicle

• Primary follicle

• Secondary Follicle

• Tertiary (mature/vesicular/graafian) follicle

• Corpus luteum

• Corpus albicans

Oogenesis

• Formation of gametes in the ovaries

• Begins before birth

• Mucosa (inner)

• Muscularis

• Serosa (outer)

What are the 3 layers of the uterine tubes (fallopian tubes)?

Major areas of the uterus

• Body

• Fundus

• Isthmus

• Cervix

• Cervical canal

• Perimetrium (outer)

• Myometrium

• Endometrium (inner)

What are the 3 layers of the uterus?

• Stratum functionalis

• Stratum basalis

The endometrium has two layers called…

Stratum Functionalis

This layer of the endometrium sheds during menstruation.

Stratum Basalis

This permanent layer in the endometrium gives rise to a new stratum functionalis after each menstruation.

Endometrium

Highly vascularized, secretory epithelium that provides the oxygen and nutrients needed otherwise sustain a fertilized egg.

Myometrium

Thick smooth muscle layer that supports the uterine wall during pregnancy and contracts to expel the fetus at birth.

Oxytocin

What hormone stimulates uterine contractions during labor?

Endometriosis

Growth of endometrial tissue outside of the uterus

Vagina

• Passageway for birth, menstrual flow & intercourse

• Wall consists of 3 layers

• Mucosa (inner)

• Muscularis

• Adventitia (outer)

What are the 3 layers of the vagina?

External Genitalia (Vulva)

• Mons pubis

• Labia majora

• Labia minora

• Clitoris

• Vestibule

• Bulb of Vestibule

• Paraurethral (Skene’s) glands

• Greater Vestibule (Bartholin’s) glands

Mons pubis

Rounded mass of fatty tissue overlaying pubic symphysis

Labia Majora

Homologous to scrotum

Labia Minora

Homologous to spongy (penile) urethra

Citoris

Homologous to glans penis

Vestibule

External urethral orifice, openings of several ducted glands & vaginal orifice

Bulb of the vestibule

• Homologous to the erectile tissues of the penis

• Elongated masses of erectile tissue on either side of vaginal orifice

Paraurethral (Skene’s) glands

Secrete mucus homologous to prostate gland

Greater Vestibular (Bartholin’s) Glands

Secrete mucus homologous to the bulbourethral gland

Mammary Glands

• Modified sweat glands that produce milk (lactation)

• Lobes (15-20) → Lobules → Alveoli

• Lactiferous ducts

• Areola

• Suspensory Ligaments

GnRH

Which hormone controls female reproductive cycle and stimulates secretion of FSH & LH?

Estrogen

• Promote development of female reproductive structures

• Increase protein anabolism

• Lower blood cholesterol

• Moderate levels inhibit release of GnRH, FSH, and LH

Progesterone

• Works with estrogens to prepare endometrium for implantation

• Prepares mammary glands to secrete milk

• Inhibits release of GnRH & LH

Relaxin

• Inhibits contractions of uterine smooth muscle

• During labor, increases flexibility of pubic symphysis and dilates uterine cervix

Inhibin

Inhibits release of FSH and, to a lesser extent, LH

Ovarian Cycle

• Follicular phase

• Ovulation

• Luteal phase

Uterine Cycle

• Menstruation

• Proliferative phase

• Secretory phase

Perimenopause

• Time near menopause

• May have irregular or skipped periods

Menopause

• Stopped having monthly menstrual cycles for one year

• Typically between 45-55 years

• Some atrophy of reproductive organs and breasts

• Decrease in vaginal wall thickness and uterus shrinking

• Hot flashes with periodic elevation in body temperature

• Possibly thinning scalp hair and increased facial hair

• Increased risk of osteoporosis and heart disease

• Symptoms are sometimes treated with hormone replacement therapy

Men with decreased testosterone levels in the 50s

• Due to decreased number of interstitial cells

• Decline more gradually than woman’s hormone drop

• Most men with few symptoms

• Some with mood swings, decreased sex drive, hot flashes

Prostate enlargement

• Experienced by most men with age

• Can interfere with sexual and urinary functions

Erectile dysfunction

• Inability to achieve or maintain erection

• Associated with aging, other risk factors