Ch 27 - The Reproductive System (male and female)

Testes (BEGINNING OF MALE REPRODUCTIVE SYSTEM SECITON)

sperm-producing male gonads that lie within the scrotum

• at birth, the testes contains stem cells

it is a paired organ in the scrotum that is partially covered by the tunica vaginalis

What is sperm delivered through?

1. Epididymis

2. ductus deferens

3. ejaculatory duct

4. urethra

Ejaculatory duct

a short passageway for sperm to go to the urethra

• they arise from the junction of the duct from the seminal vesicle and the ampulla of the ductus deferens

Accessory sex glands

seminal glands, prostate, bulbo-urethral gland

Androgens

male reproductive hormones

• the main male reproductive hormone is testosterone

Scrotum

a sac of loose skin and underlying subcutaneous tissues that connects the testes

Tunica Vaginalis

outermost layer of the testes

• it partially covers the testes

Tunica albuginea

connective tissue capsule that is internal to the tunica vaginalis

• it extends inward to form septa that create compartments in the testes

• it forms extensions (septae) that separates testes into lobules

Seminiferous tubules

carry sperm produces within them (spermatogenesis) out of the testes

spermatogenesis

development and maturation of sperm cells

• it begins with a spermatogonia (diplod stem cells) differentiating into diploid primary spermatocytes

Spermatogenic cells differentiation sequence

1. Spermatogonium (2n) stem cell

2. Primary spermatocyte (2n) → beings meiosis I

3. Secondary spermatocyte → completes meiosis II and produces spermatids

4. Spermatid (n)

5. Sperm cell or spermatozoon (n)

Primary spermatocytes and secondary spermatocytes

primary spermatocytes undergo and begin meiosis I to form two secondary spermatocytes (haploid cells)

secondary spermatocytes divide into 4 spermatids during meiosis II

• spermatogenesis produces 4 functional stem cells

Mitosis, meiosis, and spermatogenesis sequence

1. Spermatogonium (immature stem cells present at birth) undergo mitosis to split into diploid (2n) primary spermatocyte cells and precursor stem cells

2. Primary spermatocyte starts meiosis I, splitting into two haploid (n) secondary spermatocytes

3. The secondary spermatocytes begin meiosis II, where they contain 2 chromatids and split into four haploid (n) spermatids

4. Then, during spermatogenesis, the spermatids develop physical features in sperm cells and become spermatozoa

Sustenatcular cell nucleus

creates androgen binding proteinsS

Sperm

designed to reach secondary oocyte to achieve fertilization and create a zygote

• the head of the sperm contains a nucleus with 23 chromosomes

• the acrosome covers the head and contains enzymes to help with fertilization

• the neck contains centrioles that form the microtubules that make up the rest of the tail

• the middle piece contains mitochondria that make ATP for locomotion (able to move around) of the sperm

• the principal piece and end piece make up the tail used for movement

what controls testicular function?

hormones

• GnRH, LH, and FSH

Gonadotropin releasing hormone (GnRH)

stimulates cells in the anterior pituitary to produce LH and FSH

LH

targets Leydig (interstital cells) in the testes and stimulates testosterone production

FSH

stimulates spermogenesis

• targets sertoli (sustenacular) cells in the seminiferous tubules to promote the production of ABP (androgen binding proteins)

ABP binds to testosterone needed for spermatogenesis

Testosterone

produce several effects:

• development of male reproductive organs

• secondary sex characteristics

• spermatogenesis

• anabolism of protein in the bones and muscles

testosterone is control by negative feedback

Dihydrotestosterone

produces several effects:

• male pattern of development (before birth)

• enlargement of male sex organs and expression of male secondary sexual characteristics (starting at puberty)

• anabolism (protein synthesis)

Steps (hormones)

1. GnRH is produced by the hypothalamus and brought to the anterior pituitary where it stimulates the production and release of FSH and LH

2. after being secreted, LH stimulates testosterone secretion and FSH works with testosterone to stimulate spermatogenesis (sperm production)

3. spermatogenic cells secrete androgen binding proteins to bind with testosterone (FSH pathway) and interstitial cells secrete testosterone (LH pathway)

note: testosterone decrease the release of GnRH and LH (negative feedback)

Efferent ducts

carry the sperm from retes testis to the epididymis

• sperm mature in the epididymis and degenerated sperm cells are absorbed

• the epididymis propels sperm into the ductus (vas) deferences

Ductus (vas) deferens (pathway of sperm)

exits the tail of the epididymis and ascend through the spermatic cord into the pelvis

then, it loops over the ureter and passes over the side and down the posterior surface of the urinary bladder

Spermatic cord

ascending out of the scrotum and connects to the epididymis

• contains the ductus deferens, testicular artery, veins draining the testes, autonomic nerve, lymphatic vessels and the cremaster muscle

Urethra

duct shared by the reproductive and urinary systems

• both semen and urine pass through the urethra (in the male reproductive system)

the urethra passes through the prostate gland, deep muscles of the perineum, and the penis

• prostatic urethra

• intermediate (membranous urethra)

• spongy urethra

Accessory glands

they help with protection, motility, and fertilization

• problems with the seminal vesicle and prostate results in infertility

Seminal vesicles (glands)

secrete an alkaline viscous fluid containing fructose (monosaccharide), prostaglandins and clotting proteins

• sperm cells break down fructose for energy

Prostate

single gland that secretes slightly acidic fluid containing citric acid, proteolytic enzymes, acid phosphatase, and seminalplasminBu

Bulbourethral (Cowper’s) glands

secrete an alkaline fluid during sexual arousal that neutralizes acids from urine and mucus for lubrication

Semen

mixture of sperm and seminal fluid

• pH is around 7.2-7.7

• contains around 50-150 million sperm/mL

Penis (END OF MALE REPRODUCTIVE SYSTEM)

contains the urethra and is a passageway for semen and urine

• composed of 3 cylindrical masses: 2 corpora cavernosa and one corpus spongiosum

Ovaries (BEGINNING OF FEMALE REPRODUCTIVE SYSTEM)

female gonads that produce female gametes (ova); they are paired organs homologous to the testes

• they secrete female sex hormones: estrogen, proestrogen, inhibin, and relaxin

• they are supported by the broad ligament, ovarian ligament, and suspensory ligament

Internal genitalia

located in the pelvic caavity; include ovaries and duct system (uterine tubes, uterus, and vagina)

External genitalia

external sex organs

Layers of the ovaries

1. germinal epithelium: superficial covering of the ovaries

2. tunica albuginea: capsule of dense irregular CT below germinal epithelium

3. ovarian cortex: below tunica albuginea and consists of ovarian follicles and stromal cells

4. ovarian medulla: CT, BVs, lymphatic vessels, and nerves

Ovarian follicles

present at birth and mature at puberty

• they contain oocytes, follicular cells, and granulosa cells

primodrial follicle

tiny and are present at birth

Mature (graafian) follicles

ready to rupture and expel the secondary oocyte

• also called ovulation

Corpus luteum

after ovulation, the ruptured cell becomes the corpus luteum which secretes protestrogen, estrogens, inhibin, and relaxin

• mostly estrogen

Degenerating corpus luteum

functions after ovulation and fertilization

• if fertilization does not occur, corpus luterum degenerates into corpus albicans

maturation of follicles

primordial follicle → primary follicle → secondary follicle → mature follicle → corpus hemorrhagicum (ruptured follcile) → corpus luteum → degenerating corpus luteum → corpus albicans

oogenesis

development of oocyte

• begins in fetal stage

primary oocyte starts in meiosis I but pauses in prophase until puberty

after puberty each month, one primary oocyte completes meiosis I, divides equaly to form

1. secondary oocyte → large, functional cells with large amount of cytoplasm

2. first polar body → small cell that degenerates with mostly nucleus

secondary oocyte beings meiosis II and stops at metaphase II (secondary oocyte is released during ovulation)

• meiosis II is only completed if fertilization occurs. it produces

  • ovum: mature egg (zygote)

  • second polar body

oogenesis produces only one functional sperm cell

Uterine tubes

extend from the uterus to ovaries

• where fertilization takes place

they are the pathway for sperm to reach the ovum and for the secondary oocytes and fertilized ova to travel to the uterus

• the part of the tube closest to the ovary is the infundibulum

• fimriae project from it

• the ampulla is the widest portion of the tube

fimbriae of uterine tube

connects the uterine tube to the ovary

3 layers of the uterine tube

mucosa, muscularis, and serosa

• the simple ciliated columnar epithelium of the mucosa contains cilia that moves the fertilized ovum or secondary oocyte towards the uterus

• Peg cells in the tube secrete a fluid providing nourishment for the ovum

Uterus

muscular organs where fertilized ovum will implant

• top of the uterus is the fundus

• central portion is the body

• inferior extension into the vagina is the cervix

Three layers of the uterine wall

1. Perimetrium: outer protective layer

2. Myometrium: thick smooth muscle layer

3. Endometrium: inner lining consists of two strata

• has stratum functionalis and stratum basalis

Stratum functionalis

thick inner layer of the endometrium

• shed each month during menstruation (grows then is removed during menstruation)

Stratum basalis

deepest layer of the endometrium

• permanent and gives rise to a stratum functionalism after each menstruation

female reproductive cycle

involves oogenesis and preparation by the uterus to recieve a fertilized ovum

• ovarian cycle includes changes in ovaries that occur during and after maturation of oocyte

• uterine cycle involves changes in the endometrium that prepare it for implantation of developing embryo

Typical female cycle

lasts around 24-36 days

• average is 28 days (day 14 is ovulation)

menstrual

shedding of endometriump

preovulatory

after menstruation and before ovulation

• in ovaries: follicles grow under the influence of FSH

• in uterus: endometrium begin to thicken due to estrogen

ovulation

surge in LH trigger release of secondary oocyte from the ovary

Postovulatory

corpus luteum forms and secretes proestrogens and some estrogen

• endometrium (uterine lining) thickens more

• if fertilization does not occur, corpus luteum degenerates, progesterone level declines

FSH

begins to rise in the preovulatory phase

• stimulates growth of ovarian follicles

• estrogen gradually increases as follicles develop

estrogen

peaks before ovulation, triggering LH surge by positive feedback

the LH surge causes ovulation

luteal phase

corpus luteum is formed and functional

• proestrogen high from corpus luteum

• estrogen moderate

• FSH and LH are suppressed