Reproductive system and Development

Male reproductive structures

Menstrual cycle

Meiosis- makes gametes, 4 unique haploid gametes

Embryonic development

Hormones

Female reproductive structures

Male

Female

Fetal development

Ovarian follicles in ovaries consist of follicle cells surrounding an oocyte. The different types are for each different stage

hormone levels

effects on endometrium

Ovarian follicular stages

1st:Primordial follicle-primary oocyte-single layer of cells around oocyte.

2nd:Primary follicle-primary oocyte-single/multiple layers cuboidal granulosa cells around an oocyte

3rd:Secondary follicle-primary oocyte- multiple layers of granulosa cells surround oocyte and small antrum.

4th:Vesicular follicle- secondary oocyte- multiple layers of granulosa cells surround oocyte and large antrum.

5th:Corpus luteum-no oocyte- yellow collapsed fold of granulosa cells.

6th:Corpus albicans-no oocyte- remnant of corpus luteum, connective scar tissue

2 Ovaries-lateral to the uterus, from outside in is the germinal epithelium, tunica albuginea, cortex, and medulla.

2 Fallopian tubes: extend laterally from uterus to both ovaries.

Ampulla- expanded region medial to infundibulum where fertilization usually occurs

isthmus-medial to ampulla towards uterus, 1/3 length of tube

Infudibulum- funnel-shaped with fimbriae that enclose the ovary during ovulation

uterine part- medial to isthmus and penetrates uterus wall

Uterus/Womb- pear shaped, thick walled muscular organ.supports, protects, and nourishes the developing embryo/fetus. layers include perimetrium, myometrium, and endometrium.

Vagina- thick walled, inferiormost fibromuscular tube that is 10 cm in length. Birth canal, connects uterus to the outside of the body, passageway for menstruation

Fundus- curved superior region extending between fallopian tubes

Body of uterus- middle region, thick wall of smooth muscle

Anteverted- anterosuperiorly across the superior surface of the bladder.
Retroverted- posterosuperiorly, projecting towards the rectum

isthmus-constricted inferior region of the body

Cervix- narrow inferiormost portion of the uterus projects into vagina. includes Internal os, cervical canal, and external os.

250 lobules in each teste, the testes are in a sac called the scrotum which provides cooler environment needed for sperm development

Rete testis receive sperm from seminiferous tubules and merge to form efferent ductules (12-15 each teste).

Seminiferous tubules- thin and elongated. 4 per lobule. contain sustentacular cells and germ cells.

efferent ductules drain into the epididymis. the epididymis stores sperm until they are fully mature.

interstitial spaces- spaces surrounding seminiferous tubules. interstitial cells are in this space, which produce androgens

Penile urethra- transports semen from both ejaculatory ducts to the outside of body

Luteinizing LH- from anterior pituitary- stimulates ovulation

Estrogen- from ovarian follicles before ovulation/corpus luteum after ovulation/placenta during pregnancy. initiates and maintains growth of endometrium

Follicle-stimulating FSH- from anterior pituitary. stimulates development and maturation of ovarian follicles

progesterone- from corpus luteum/ placenta during pregnancy. causes increase in blood vessel distribution, uterine gland size, and nutrient production

Gonadotropin-releasing GnRH- from hypothalamus. stimulates ant.pituitary to secrete FSH & LH

Inhibin- from ovarian follicles. inhibits FSH secretion to prevent excessive follicular development

Follicle-stimulating FSH- from anterior pituitary. stimulates interstitial cells to secrete testosterone

testosterone- stimulates spermatogenesis, inhibits GnRH secretion

Gonadotropin-releasing GnRH- from hypothalamus. stimulates ant.pituitary to secrete FSH & LH

Inhibin-inhibits FSH secretion

Days 6-13 Follicular phase: estrogen and inhibin inhibit the hypothalamus & anterior pituitary which causes a drop in FSH. 1 follicle continues to mature and produce estrogen

Day 14 Ovulation: increase in estrogen above threshold stimulates hypothalamus & anterior pituitary causing LH surge inducing ovulation

Days 1-5 Follicular phase: GnRH stimulates FSH and LH secretion, some ovarian follicles develop and produce estrogen

Days 15-28 Luteal phase: Corpus lutem forms & secretes large amounts of estrogen, progesterone, and inhibin. all of these comined inhibit GnRH FSH and LH secretion.

Days 1-5 Menstrual phase: functional layer of the endometrium is shed

Days 6-14 proliferative phase: functional layer of endometrium rebuilds

Day 15-28 Secretory phase: functional layer sloughs off

Progesterone stimulates uterine lining growth but if an oocyte is not fertilized, the corpus lutem regresses and hormone levels drop

Ductus deferens- sperm leaves epididymis and enters the vas deferens, thick walled tube

Ampulla of vas deferens- unites with the proximal region of the seminal vesicle to form the ejaculatory duct (1-2 cm long) which conducts sperm and seminal fluid towards urethra

Prostate gland- walnut shaped 20grams. inferior to bladder. secretes milky fluid that is weakly acidic and rich in citric acid, seminalplasmin, and PSA.

Bulbourethral glands- secrete clear mucus that protects the urethra and serves as lubricant during intercourse

Seminal vesicles- lateral to ampulla. secrete a viscous whitish-yellowish alkaline fluid containing both fructose and prostaglandins

Week 4: basic human body plan is established, cylindrical embryo, limb buds appear, derivatives of the three germ layers begin to form, 4mm

Week 5-8: head enlarges, eyes ears and nose appear, mandibular arch forms, major organ systems formed , 30mm

Week 3: establishment of the three primary germ layers through the process of gastrulation. 1.5mm

Weeks 21-38: body gains major amount of weight, brows and lashes appear, subcutaneous fat is deposited, eyelids open, Testes descend into scrotum (male), 53cm, 2.5-4.5 kg

Weeks 17-20: muscle movements become stronger and frequent, lanugo and vernix caseosa covers skin, limbs near final proportions, 19 cm, 454 grams

Weeks 13-16: body grows rapidly, limbs become more proportionate, brain and skull continue to enlarge, ossification in skeleton continues, 14cm, 170 grams

Weeks 9-12: primary ossification centers appear in most bones, reproductive organs begin to develop, brain grows, body gets longer, palate of mouth develops, 9cm, 28 grams

Mesoderm- middle layer,muscles, bones, some organs

Endoderm- digestive tract, inferior layer

Ectoderm- superior layer, Skin, nervous system

Spermatogenesis

Oogenesis

Spermiogenesis: newly formed spermatids differentiate to become anatomically mature sperm.

Meiosis II: originates with the secondary spermatocytes and produces spermatids

Meiosis I: begins in the diploid primary spermatocytes. haploid cells produced during meiosis I are secondary spermatocytes

Mitotic division- spermatogonia are primordial germ stem cells that contain 23 pairs of chromosomes.mitotic divisions of spermatogonia produce a new germ cell and a committed cell calked a primary spermatocyte

Childhood- Ovary is inactive, houses primordial follicles. meiosis I arrested.

Monthly from puberty to menopause- about 20 primordial follicles mature into primary follicles every month. some mature into secondary follicles.

Before birth- Oogonia are diploid cells (origin of oocytes) containing 23 pairs of chromosomes. mitotic divisions of oogonia produce primary oocytes. primary oocytes begin meiosis but stop at prophase I

usually only 1 secondary follicle matures into a vesicular follicle. primary oocyte completes meiosis I producing a polar body and a secondary oocyte (23 chromosomes) which is paused in meiosis metaphase II

if secondary oocyte is fertilized then it will complete the 2nd meiotic division and becomes an ovum. if its not fertilized then it degenerates

Meiosis 2

Meiosis I

Metaphase 1- chromosomes pairs line up forming a double line of chromosomes

Antaphase1- separate pairs of chromosomes to opposite sides of cell (reduction division)

Prophase 1- nuclear membrane goes away, Crossing over occurs between homologous maternal and paternal chromosomes (tetrad)

Telephase 1- 2 new haploid nuclei, each containing 23 chromosomes

Anaphase2- sister chromatids of each replicated chromosome are pulled apart, sister chromatids migrate to opposite ends

Metaphase2- replicated chromosomes align along the equator of the cell

Telophase2- single chromosomes arrive at opposite ends of cell and nuclear membrane reforms

Prophase2- nuclear envelop breaks down, replicated chromosomes cluster together

*Meiosis stops after T2*