Female Reproductive System

Female Reproductive System

The Highlights

Hormones of the Female Reproductive Cycle

• Control the reproductive cycle

• Coordinate the ovarian and uterine cycles

Hormones of the Female Reproductive Cycle

• Key hormones include:– FSH

• Stimulates follicular development

– LH • Maintains structure and secretory function of corpus

luteum

– Estrogens • Have multiple functions

– Progesterones • Stimulate endometrial growth and secretion

Female Reproductive Organs

• Ovary: female gonad• Uterine Tubes (fallopian tube, oviduct)

- three parts: infundibulum, ampulla, isthmus

Figure 28.13

The Female Reproductive System in Midsagital View

Figure 28.14a, b

The Ovaries and Their Relationships to the Uterine Tube and Uterus

The Uterus• Muscular organ

– Mechanical protection– Nutritional support– Waste removal for the developing embryo and fetus

• Supported by the broad ligament and 3 pairs of suspensory ligaments

Uterine Wall Consists of 3 Layers:

• Myometrium – outer muscular layer

• Endometrium – a thin, inner, glandular mucosa

• Perimetrium – an incomplete serosa continuous with the peritoneum

• The site of implantation of developing embryo• And 3 parts: fundus, body, and cervix

Female Accessory Sex Organs: Uterus

• Uterine endometrium has two layers:

- basal layer

- functional layer: built up and shed each cycle

Figure 28.18c

The Uterus

Figure 28.19b

The Uterine Wall

Figure 28.20

The Uterine CycleTo be discussed below

Functions of the Ovary

• Production of a mature oocyte, capable of fertilization and embryonic development.

• Production of ovarian steroids (estradiol, progesterone).

• Production of gonadal peptides (inhibin, activin).

Structural Organization of the Ovary

• The main functional unit of the ovary is the follicle.

• Follicles are composed of the oocyte, granulosa cells, and theca cells.

Stages of Follicular Growth

• Follicles are present in a number of different stages of growth:- primordial follicles (resting)- primary, secondary, and antral follicles- preovulatory (Graafian) follicles

The Corpus Luteum

• After the preovulatory follicle ovulates (releases its egg), it forms the corpus luteum.

FEMALE REPRODUCTIVE SYSTEM The Ovarian Cycle

OVARY

3 to 5 million OOGONIA differentiate into PRIMARY OOCYTES during early development

OOCYTES becomes surrounded by squamous (follicular) cells to become PRIMORDIAL FOLLICLES

most PRIMORDIAL FOLLICLES undergo atresia leaving 400,000 at birth

oocytes at birth arrested at Meiosis I (prophase)oocytes at birth arrested at Meiosis I (prophase)

FEMALE REPRODUCTIVE SYSTEM

OVARY

THREE STAGES OF OVARIAN FOLLICLES CAN BE IDENTIFIED FOLLOWING PUBERTY:(each follicle contains one oocyte)

(1) PRIMORDIAL FOLLICLES

- very prevalent; located in the periphery of the cortex

- a single layer of squamous follicular cells surround the oocyte

(2) GROWING FOLLICLES

- three recognizable stages:

(a) early primary follicle

(b) late primary follicle(c) secondary (antral) follicle

(3) MATURE (GRAAFIAN) FOLLICLES- follicle reaches maximum size

OO

GEN

ESIS


OVARIAN FOLLICLES

(1) PRIMORDIAL FOLLICLES

(2) GROWING FOLLICLES

(a) early primary follicle

- follicular cells still unilaminar but now are cuboidal in appearance

- oocyte begins to enlarge

(b) late primary follicle

- multilaminar follicular layer; cells now termed granulosa cells

- zona pellucida appears; gel-like substance rich in GAGs

- surrounding stromal cells differentiate into theca interna and theca externa

(b) secondary (antral) follicle

- cavities appear between granulosa cells forming an antrum

- follicle continues to grow

- formation of cumulus oophorus and corona radiata

(3) MATURE (GRAAFIAN) FOLLICLES


HORMONAL REGULATION OF OOGENSIS AND OVULATION

HYPOTHALAMUS release of GnRF which stimulates release of LH and FSH from the adenohypophysis (ANTERIOR PITUITARY)

Neuroendocrine Regulation of Ovarian Functions

OVARY

E2, P

inhibin,

activin

Ovulation

Pituitary

GnRH

FSHLH

CNS

hypothalamus

Follicle

Development

Luteinization

Effects of GnRH on Gonadotropins

• GnRH is released in a pulsatile manner, stimulating the synthesis and release of LH and FSH.

• GnRH acts through its receptor on the pituitary gonadotroph cells, stimulating production of phospholipase C.

• Recall that IP3 pathway causes gonadotropin release, while the DAG/PKC pathway causes gonadotropin synthesis.

Actions of FSH on Granulosa Cells

FSH

Gs

AC

ATP

cAMP

PKA

CREB CRE

Steroidogenic

enzymes

LH Receptor

Inhibin Subunits

Plasminogen

activator

Gene Expression

LH

androgens

estradiol

Theca cells

Granulosa cells

aromatase

FSH

Ovarian Estradiol Production

Regulation of Progesterone Production

• Progesterone is produced from theca cells, mature granulosa cells, and from the corpus luteum.

• In this case, gonadotropins induce expression of

- steroidogenic acute regulatory protein

- P450 side chain cleavage

• Estradiol also has important actions in a number of other tissues:- causes proliferation of uterine endometrium- increases contractility of uterine myometrium- stimulates development of mammary glands- stimulates follicle growth (granulosa cell proliferation)- effects on bone metabolism, hepatic lipoprotein production, genitourinary tract, mood, and cognition

• Effects are mediated through the intracellular estrogen receptors (alpha and beta), and possible membrane effects.

Actions of Estradiol

Actions of Progesterone

• Progesterone exerts positive and negative feedback effects on gonadotropin synthesis and release.

• Progesterone also acts on many tissues:- stimulates secretory activity of the uterine endometrium- inhibits contractility of the uterine myometrium- stimulates mammary growth

• The actions of progesterone are mediated through an intracellular P receptor, which acts as a transcription factor.

FEMALE REPRODUCTIVE SYSTEM The Menstrual Cycle


FOLLICULAR PHASE LUTEAL PHASEOVULATION

10-20 primordial follicles begin to develop in response to FSH and LH levels

FSH and LH stimulate theca and granulosa production of estrogen and progesterone

surge of LH induces ovulation

theca and granulosa cells transform into the corpus luteum and secrete large amounts of progesterone

if fertilization does not occur, corpus luteum degenerates ... if fertilization does occur, HCG released from the embryo maintains corpus luteum

FEMALE REPRODUCTIVE SYSTEM The Menstrual Cycle


OVULATION:

sharp surge in LH with simulataneous increase in FSH

Meiosis I resumes; oocyte and surrounding cumulus break away and are extruded

oocyte passes into oviduct

ECTOPIC IMPLANTATIONS

The Menstrual Cycle

• Women have ovulatory cycles of about 28 days in length.

• Day 1 of the cycle is defined as the first day of menstruation.

• There are two phases of the cycle, named after ovarian and uterine function during that phase:- first two weeks: follicular or proliferative stage- second two weeks: luteal or secretory stage

• The preovulatory gonadotropin surges occur in the middle of the cycle (around day 14).

The Menstrual Cycle: The Ovary

• Follicular phase: small antral follicles develop, a dominant follicle is selected and grows to the preovulatory stage.

• Midcycle: the gonadotropin surges cause ovulation of the dominant follicle.

• Luteal phase: the corpus luteum forms and becomes functional, secreting large amounts of progesterone, followed by estradiol (results in negative feedback, not positive feedback, because P increases before E2).

• If pregnancy does not take place, the corpus luteum regresses, and P and E2 levels decrease.

• Proliferative stage: increasing estradiol levels stimulate proliferation of the functional layer of the uterine endometrium.- Results in increased thickness of the endometrium.- Increased growth of uterine glands (secrete mucus) and uterine arteries.

• Secretory stage: progesterone acts on the endometrium.- uterine glands become coiled and secrete more mucus- uterine arteries become coiled (spiral arteries)

The Menstrual Cycle: The Uterus

The Menstrual Cycle: The Uterus

• If pregnancy doesn’t occur, P and E2 levels decrease at the end of the secretory stage.

- vasospasm of arteries causes necrosis of tissue

- loss of functional layer with bleeding of uterine arteries (menstruation)


UTERUS

ENDOMETRIUM

TWO LAYERS:

undergoes cyclic changes which prepare it for implantation of a fertilized ovum

(1) FUNCTIONAL LAYER (stratum functionalis)

(2) BASAL LAYER (stratum basale)

- BORDERS UTERINE LUMEN- SLOUGHED OFF AT MENSTRATION

- RETAINED AT MENSTRATION- SOURCE OF CELLS FOR REGENERATION OF

FUNCTIONAL LAYER

- CONTAINS UTERINE GLANDS

STRAIGHT AND SPIRAL ARTERIESSTRAIGHT AND SPIRAL ARTERIES


HORMONAL REGULATION OF UTERINE CYCLE

(1) PROLIFERATIVE PHASE concurrent with follicular maturation and influenced by estrogens

(2) SECRETORY PHASE concurrent with luteal phase and influenced by progesterone

(3) MENSTRUAL PHASE commences as hormone production by corpus luteum declines

Male Reproductive System

The Highlights

The Male Reproductive System in Midsagital View

Figure 28.1

MALE REPRODUCTIVE SYSTEM

TESTIS

- thick connective tissue capsule- connective tissue septa divide

testis into 250 lobules

TUNICA ALBUGINEA

(1) SEMINIFEROUS TUBULES(1) SEMINIFEROUS TUBULES

- each lobule contains 1-4 seminiferous tubules and interstitial connective tissue

- produce sperm

INTERSTITIAL TISSUE

- contains Leydig cells which produce testosterone

(2) RECTUS TUBULES(2) RECTUS TUBULES

(3) RETE TESTIS(3) RETE TESTIS

(4) EFFERENT DUCTULES(4) EFFERENT DUCTULES

(5) EPIDIDYMIS(5) EPIDIDYMIS


SERTOLI CELLS

SERTOLI CELLS

SPERMATOGONIASPERMATOGONIA

1º SPERMATOCYTE1º SPERMATOCYTE

2º SPERMATOCYTE2º SPERMATOCYTE

SPERMATIDSSPERMATIDS

SPERMATOGENESISSPERMATOGONIASPERMATOGONIA 1º SPERMATOCYTE1º SPERMATOCYTE 2º SPERMATOCYTE2º SPERMATOCYTE SPERMATIDSSPERMATIDS

SERTOLI CELLS:SERTOLI CELLS:

- columnar with adjoining lateral processes- columnar with adjoining lateral processes

- Sertoli-Sertoli junctions divide seminiferous tubules into basal and adluminal compartments

- Sertoli-Sertoli junctions divide seminiferous tubules into basal and adluminal compartments

- extend from basal lamina to lumen- extend from basal lamina to lumen

Basal Lamina

2n2n 2n2nSpermatogonia (stem cells)

2n2nmitosis

Daughter cell Type A spermatogonium remain at basal lamina as a precursor cell

Daughter cell Type B Spermatagonium

Moves to adluminal compartment

nn

nn 1° spermatocyte

nn

Meiosis I completed

2° spermatocyte

nn nn nn nn Early spermatids

n n n n Late spermatids

Meiosis II


SPERMATOGENESISTHREE PHASES:

(1) Spermatogonial Phase (Mitosis)

(2) Spermatocyte Phase (Meiosis)

(3) Spermatid Phase (Spermiogenesis)

- acrosome formation; golgi granules fuse to form acrosome that contains hydrolytic enzymes which will enable the spermatozoa to move through the investing layers of the oocyte

- flagellum formation; centrioles and associate axoneme (arrangement of microtubules in cilia)

- changes in size and shape of nucleus; chromatin condenses and shedding of residual body (cytoplasm)


HORMONAL REGULATION OF MALE REPRODUCTIVE FUNCTION

HYPOTHALAMUS REGULATES ACTIVITY OF ANTERIOR PITUITARY (ADENOHYPOPHYSIS)

ADENOHYPOPHYSIS SYNTHESIZES HORMONES (LH and FSH) THAT MODULATE ACTIVITY OF SERTOLI AND LEYDIG CELLS

Luteinizing Hormone (LH): stimulates testosterone production by Leydig cells

Follicle Stimulating Hormone (FSH): stimulates production of sperm in conjunction with testosterone by regulating activity of Sertoli cells

SERTOLI CELLS STIMULATED BY FSH AND TESTOSTERONE RELEASE ANDROGEN BINDING PROTEIN WHICH BINDS TESTOSTERONE; THEREBY INCREASING TESTOSTERONE CONCENTRATION WITHIN THE SEMINIFEROUS TUBULES AND STIMULATING SPERMATOGENESIS

SERTOLI CELLS STIMULATED BY FSH AND TESTOSTERONE RELEASE ANDROGEN BINDING PROTEIN WHICH BINDS TESTOSTERONE; THEREBY INCREASING TESTOSTERONE CONCENTRATION WITHIN THE SEMINIFEROUS TUBULES AND STIMULATING SPERMATOGENESIS

Female Reproductive System

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