Lesson 10

Major reproductive organs

gonads (testes and ovaries)

Testes

male reproductive organ

Ovaries

female reproductive organ

Gonads produce…

sex cells and hormones

Male gonads produce…

sperm and testosterone

Female gonads produce…

ova (eggs) and estrogen and progesterone

External structures of male reproductive system

external genitalia (penis, scrotum)

Penis

composed of 3 cylinders of erectile tissue, 2 dorsal cylinders (corpora cavernosa) and 1 ventral cylinder (corpus spongiosum) - 2 major parts as glans penis and body

Glans penis

tip of the penis - covered by prepuce/foreskin

Body of penis

shaft of the penis

Scrotum

contains the testes - regulates temperature to optimize sperm production (94 F/34 C)

Internal structures of male reproductive system

duct system - epididymis, ductus deferens/vas deferens (sperm duct), ejaculatory duct, urethra

Duct system

accessory structures that form the ducts that carries sperm from testes to external environment

Epididymis

located on superior and posterolateral area of the testes - site where immature sperm cells complete maturation process

Ductus deferens/vas deferens (sperm duct)

along with blood vessels and nerves, they are enclosed in connective tissue sheath called spermatic cord - connects the epididymis to ejaculatory duct at ampulla

Ejaculatory duct

propels sperm through prostate gland to urethra during ejaculation

Urethra

runs the length of penis, common path of both the urinary and reproductive system - has 3 parts (prostatic, intermediate part (membranous) and spongy)

Accessory glands of male reproductive system

produces seminal fluid that bathes sperm - includes prostate gland, seminal glands/vesicles, bulbourethral glands

Prostate gland

inferior to bladder, encircles and secretes milky fluid into urethra to activate sperm

Seminal glands/vesicles

posterior to bladder - joins ductus deferens to form ejaculatory duct - produces alkaline secretion containing fructose and other nutrients which supplies energy to sperm cells or promotes fertilization - produces 60% of seminal fluid

Bulbourethral glands

inferior to prostate - produces thick, clear, alkaline mucus that drains into membranous urethra (washes out urine during ejaculation of semen (sperm and seminal fluid))

Testes

gonads that produce sperm and testosterone

Exterior of testes

covered by tunica albuginea (dense connective tissue), extends into inferior (forms many septa) to divide testis into lobules containing seminiferous tubules and rete testis

Seminiferous tubules

site of sperm production - interstitial cells between tubules produce testosterone

Rete testis

carries sperm from seminiferous tubules to epididymis

External structures of female reproductive system

includes external genitalia (vulva) and mammary glands

Mons pubis

overlies pubic symphysis

Labia majora

homologous to scrotum in males

Labia minor

enclose vestibule region containing clitoris, urethral orifice, vaginal orifice

Ciltoris

homologous to penis in males, covered by prepuce of the clitoris

Urethral orifice

part of the urinary system - separate from the reproductive system

Vaginal orifice

external opening that leads into the internal reproductive structures - hymen and greater vestibular glands

Hymen

thin fold of mucous membrane, closes vaginal opening

Greater vestibular glands

flanks vaginal opening, produces lubricants during coitus

Internal structures of female reproductive system

ligaments and organs

Ligaments of female reproductive system

all organs except ovaries are suspended by ligamentous folds of peritoneum

Broad ligaments

mesometrium, mesosalpinx, mesovarium

Mesometrium

secures uterus

Mesosalpinx

secures uterine tubes

Mesovarium

anchors ovaries posteriorly

Round ligaments

secures uterus to labia majora

Uterosacral ligaments

secures inferior uterus to the sacrum

Ovarian ligament

anchors ovaries to uterus, supported by suspensory ligaments

Suspensory ligaments

anchors ovaries laterally

Organs of female reproductive system (internal)

vagina, uterus, uterine/fallopian tubes, ovaries

Vagina

birth canal connecting vestibule to uterus

Uterus

muscular organ located between bladder and rectum

Uterine wall layers include

endometrium, myometrium, serosa

Endometrium

interior layer composed of a functional layer (stratum functionalis)that is formed by basal layer/stratum basalis - functional layer is the usual site of egg implantation and is discarded during menses

Myometrium

muscular medial layer of uterus

Serosa

protective outer layer of uterus

Major structures of uterus

cervix, body and fundus

Cervix

inferior uterus

Body of uterus

major portion of uterus

Fundus

superior uterus

Uterine/fallopian tubes

located at superolateral region of uterus extending toward ovaries - distal end closest to ovaries have fimbriae finger-like projections, ampulla is the widest, longest portion, isthmus located medially and is narrow with thick-walled - uterine tube is the usual site of egg fertilization by sperm

Ovaries

site of female gamete (egg) development and estrogen production (both in follicles) - egg ejection during ovulation (follicle forms corpus luteum to produce progesterone and some estrogen)

Mammary glands

located anterior to pectoral muscles - growth starts in puberty, caused by estrogen production

External features of mammary glands

areola and nipple

Areola

pigmented area surrounding nipple

Nipple

site of milk release in lactation

Internal features of mammary glands

lobes

Lobes

15-25 lobes composed of connective and fatty tissue - lobes contain lobules containing milk producing alveoli (milk formed here passes through lactiferous ducts and stored in lactiferous sinus)

Meiosis

occurs in gonads - sperm and eggs contain haploid complement

Haploid complement

½ normal chromosome number (2n) - has 23 chromosomes

Fusion of sperm (n) and egg (n) restores…

the 23 pairs of chromosomes (2n)

The fertilized egg (2n) has…

23 chromosome pairs (23rd pair = sex chromosomes)

Fertilized egg is…

diploid

Mitosis occurs in…

somatic cells (most cells in the body) - chromosome number is conserved - daughter cells have same number of chromosomes as the parent cell (2n, diploid)

Meiosis consists of…

2 nuclear divisions - meiosis I and meiosis II - end of meiosis II yields 4 daughter cells

Meiosis I

• chromosomes undergo semi-conservative replication - occurs in interphase (before meiosis)

• in the process of synapsis, homologous chromosomes (containing genes from the same trait) line up side to side to form pairs called tetrads

• 23 tetrads line up at equator and homologous chromosomes can exchange genetic material with its pair at points of crossover/chiasmata

• after crossover event, dyads move to opposite ends during anaphase

• cytokinesis occurs to yield 2 daughter cells after telophase

Meiosis II

• genetic material does not replicate here - each daughter cell of meiosis I has only ½ the homologous chromosomes

• each daughter cell forms 2 daughter cells (2 daughter cells from meiosis I each produces 2 daughter cells to yield a total of 4 daughter cells by the end of meiosis II)

Spermatogenesis

starts at puberty - occurs in seminiferous tubules of testes from spermatogonia (primary stem cells)

Spermatogonia

under FSH influence during puberty, produces primary spermatocytes (through mitosis) - primary spermatocytes then undergo meiosis to yield spermatids

Spermatids undergo spermiogenesis to form…

functional sperm

Oogenesis

occurs in ovary (ovum encased in follicle by follicle/granulosa cells) - influenced by gonadotropic hormones from anterior pituitary - begins with oogonia (primary stem cells) in developing female fetus (does not begin in puberty)

Oogonia

undergoes thousands of mitotic divisions in fetal development - become encapsulated by cells to form primordial follicles of ovaries

Primary oocytes

by birth, encapsulated oogonia grows into primary oocyte (arrested at prophase of meiosis I)

At puberty, FSH causes…

one/more follicle maturation

Primary follicle

formed as follicle grows around primary oocyte - follicle cells produces estrogens

Secondary follicle

primary oocyte maturing - estrogen produced feedback to stop gonadotropin release by anterior pituitary

Vesicular (antral) follicle

primary oocyte completes meiosis I producing secondary oocyte (arrested at metaphase II) and first polar body - the mature follicle releases secondary oocyte enclosed corona radiata (formed by granulosa cells) when anterior pituitary suddenly increases LH release - turns into corpus luteum (produces progesterone and estrogen) - if LH levels drop, corpus luteum degenerates and replaced by scar tissue (corpus albicans)

Upon sperm fertilization of the secondary oocyte…

meiosis II proceeds - ovum (2n) and second polar body produced

Menstrual cycle

controlled by ovary (estrogen/progesterone) - occurs 14 days after ovulation - divided into 3 phases (menstrual, proliferative, secretory)

Menstrual (menses) phase

day 1-5 where functional layer of endometrium sloughs off/bleeding occurs

Proliferative phase

day 6-14 where estrogen from growing follicle causes endometrium repair, glands and blood vessels proliferate and endometrium thicken

Secretory phase

day 15-28 where corpus luteum progesterone causes increase glands and vascular supply in endometrium - if embryo present, embryo will produce LH to maintain corpus luteum