Reproductive System

meiosis

-gonads produce hormones and gametes (sex cells)

-testes: male gonads, produce sperm

-ovaries: female gonads, produce oocytes

-sex cells have 1 set of genetic instructions on 23 chromosomes (2 sets of 46)

-consists of two divisions: meiosis 1 & meiosis 2

X; Y

all ova carry an __, and half of sperm carries an X while the other half carries an __

the male (sperm)

what determines the sex of an embryo?

meiosis (cont.)

-consists of two successive divisions

-prior to this process, each chromosome replicates and contains 2 DNA strands (chromatids)

-cells are diploid (containing 2 sets of chromosomes in 23 pairs)

meiosis 1

-separates homologous pairs of chromosomes

-results in haploid cells (23 chromosomes, 1 from each homologous pair)

-prophase 1: cross over occurs to produce chromosome with genetics from both parents

-metaphase 1: chromosome pairs line up on midline

-anaphase 1: chromosome pairs separate, each daughter cell receives 1 replicated member of each pair

-telophase 1: cell divides forming 2 new haploid daughter cells; each new cell contains 23 individual chromosomes with 2 chromatids

meiosis 2

-begins after telophase 1 and is similar to mitosis

-prophase 2: chromosomes condense and reappear, still replicated

-metaphase 2: replicated chromosomes attach to spindle fibers along midline

-anaphase 2: centromeres separate and chromatids are now considered chromosomes

-telophase 2: each of 2 cells produced in meiosis 1 divides into 2 daughter cells

-this division ends with each sex cells having 1 set of genetic instructions, or 23 chromosomes (compare this to 2 sets of 46 chromosomes in other cells)

male primary sex organs

-2 testes

-produce sperm cells (spermatozoa) and sex hormones

male secondary sex organs

-other internal and external sex organs

-secrete male sec hormones

-transport sperm and secretions to outside of body

descent of testes

-male fetuses originate testes from tissue masses behind parietal peritoneum, near the kidneys

-usually 1 to 2 months before birth, testosterone triggers this process

-gubernaculum: guides testes down through inguinal canal

tunica albuginea

-tough, fibrous capsule enclosing each testis

-structure of testes

lobules

-compartments in testis, separated by connective tissue septa

-structure of testes

seminiferous tubules

-highly coiled tubules inside lobules, lined with spermatogenic cells

-structure of testes

interstitial cells

-lie between seminiferous tubules, produce & secrete male sex hormones

-structure of testes

rete testis

-channels that transport sperm from testis to epididymis

-structure of testes

epididymis

-coiled tube on top of testis that transport sperm from rete testis to ductus deferens

-promote maturation of sperm cells

-structure of testes

male internal accessory organs

-nurture and transport sperm cells

-consist of: epididymis, ductus deferens, ejaculatory duct, seminal vesicles, prostate gland, bulbourethral gland, urethra

ductus deferens

-muscular tubes that are part of the spermatic cord

-each extends from epididymis to the ejaculatory duct

seminal vesicles

-each is attached to a ductus deferens near base of bladder

-secretes alkaline fluid to regulate pH, secretes fructose and prostaglandins

-contents empty into ejaculatory duct

-contributes to most of volume of semen

prostate gland

-surrounds proximal portion of urethra

-composed of tubular glands in connective tissue, also contains smooth muscle

-secretes thin, milky, alkaline fluid

-contributes to volume of semen

bulbourethral (Cowper’s) glands

-inferior to prostate gland

-secretes mucus-like fluid into urethra

-fluid is released in response to sexual stimulation

-lubricates end of penis

semen

-fluid transported outside of body during ejaculation

-averages 120 million sperm cells per mL of semen

-men continue to remake sperm

-cannot live long in female reproductive tract

-slightly alkaline, pH = 7.5

-sperm cannot fertilize egg until they go through capacitation (weakens cap over sperm head called acrosome)

scrotum

-pouch of skin and subcutaneous tissue located behind penis

-sac that stores testicles

-dartos muscle: contracts and relaxes in response to temp changes so testes are a optimal temp for sperm production; ability to lift testicles during erection, divided by 2 septums

penis

-conveys urine and semen through urethra to outside of body

-specialized to become erect for insertion into vagina during sexual intercourse

-3 columns of erectile tissue: 2 corpora cavernosa & 1 corpus spongiosum

-glans penis: distal enlargment of corpus spongiosum

-prepuce: covering of glans penis, removed during circumcision

male erection

-during sexual stimulation, parasympathetic nerve impulses release nitric oxide which dilates arteries of penis

-pressure of arterial blood compresses veins

-penis swells and elongates

male orgasm

-culmination of sexual stimulation; pleasurable feeling of physiological and psychological release

-emission: movement of semen into the urethra

-ejaculation: movement of semen out of urethra

-dependent of sympathetic nerve impulses

spermatogenesis

-formation of sperm cells; meiosis reduces number of chromosomes so each sperm has 23

-sustentacular (Stertoli) cells: large cells spanning entire thickness of epithelium of tubule; support & nourish spermatogenic cells throughout their development into sperm

-spermiogenesis: development of spermatids into sperm

lumen

most mature sperm cells are found in the ______

spermatogonia → primary spermatocytes → secondary spermatocytes → spermatids → spermatozoa

sperm formation sequence

spermatogonia

during spermatogenesis, ____________ replenish themselves and also give rise to spermatocytes, which develop into sperm

sperm structure

-tiny tadpole shaped structure

-head: contains nucleus (23 chromosomes) & acrosome (cap over nucleus which has enzymes that penetrate layers around oocytes)

-body: contains many mitochondria which provide ATP for swimming

-tail (flagellum): contains microtubules enclosed in extension of cell membrane; lashing movement propels sperm toward egg

male reproductive functions

-controlled by hormones secreted by the hypothalamus, the anterior pituitary, and the testes

-hormone functions: initiate and maintain sperm cell production & oversee development and maintenance of male secondary sex characteristics

-like a chain and command

gonadotropin releasing hormone (male)

-secreted by hypothalamus

-regulates secretion of gonadotropins from anterior pituitary

leuteinizing hormone (male)

-secreted by anterior pituitary

-causes development of interstitial cells in testes, which secrete male sex hormones (testosterone)

follicle stimulating hormone (male)

-secreted by anterior pituitary

-stimulates sustentacular cells of testes to mature, proliferate, and respond to testosterone

androgens

-prevent oversecretion of GnRH and LH, such as testosterone

-male sex hormones that are produced by interstitial cells and sometimes in adrenal cortex

-testosterone is the MOST IMPORTANT one because secretion begins during fetal development, stops at birth, and then picks up again at puberty

inhibin

______ from sustentacular cells prevent oversecretion of FSH

dihydrotestosterone (DHT)

-adrogen derivative of testosterone

-acts on cells in prostate gland, seminal vesicles, external accessory organs

actions of testosterone

-prior to birth: development of male reproductive organs; descent of testes into scrotum

-during puberty: enlargement of testes, increased body hair, thickening of vocal cords, thickening of skin, increased muscular growth

female reproductive system specialized functions

-produce sex cells (oocytes) and sex hormones

-transport oocytes to site of fertilization

-provide favorable environment for developing offspring

-transport offspring to outside of body

female reproductive organs

-primary sex organs: ovaries (gonads)

-secondary sex organs: internal and external reproductive organs

fallopian tube

where does fertilization happen in females?

ovaries

-solid, oval structures that lie in lateral wall of pelvic cavity

-3 attaching ligaments: broad, suspensory, ovarian

-medulla: inner layer; contains many blood vessels, lymphatic vessels, and nerve fibers

-cortex: consists of more compact tissue; has granular appearance due to tiny masses of cells called ovarian follicles (where oocytes develop)

broad ligament

largest ligament that holds ovary in place, and is also attached to uterine tubes and uterus

suspensory ligament

holds the ovary at the upper end

ovarian ligament

rounded, cord-like thickening of the broad ligament; attaches lower end of ovary to uterus

descent of ovaries

-develop from masses of tissue posterior to parietal peritoneum, near developing kidneys

-descend to locations just inferior to pelvic brim, where they remain attached to lateral pelvic wall

-don’t go as far as testes do

primordial follicles

-primordial germ cells are called oogonia, and they develop into primary oocytes

-early in fetal development primary oocytes begin in the process of meiosis, but the process soon stops and doesn’t start again until puberty

-no new ones are produced after birth

-each egg has their own follicle, and oocyte numbers continually decline

uterine (fallopian) tubes

-where fertilization happens; transports ovulated egg to uterus

-infundibulum: end of tubes with extensions called fimbriae

-layers: inner mucosa, middle muscularis & outer covering of peritoneum

-peristaltic contractions help move secondary oocyte down this

uterus

-hollow, pear-shaped muscular organ; receives embryo and sustains it

-regions: body & cervix

-layers: endometrium (mucosa), myometrium (muscle), perimetrium (serosa)

vagina

-tube that runs between uterus and outside of body

-conveys uterine secretions, receives penis, provides passageway for offspring during birth

-vaginal orifice: partially enclosed by hymen (thin layer of tissue)

-3 layers

labia majora

-external reproductive female organ

-rounded folds of adipose tissue and skin

-enclose and protect other external reproductive organs

labia minora

-external reproductive female organ

-flattened folds between labia majora

-anterior end forms a covering around clitoris

clitoris

-external reproductive female organs

-small projection between labia minora and anterior end of vulva

-corresponds to male penis; composed of 2 columns or erectile tissue

vestibule

-external reproductive female organs

-space between labia minora, encloses the vaginal and urethral openings

-vestibular glands: secrete mucus into vestibule during sexual stimulation

female erection

-erectile tissue in clitoris and around vaginal entrance respond to sexual stimulation

-nitric oxide dilates arteries in erectile tissue, expanding vagina

female lubrication

-sexual stimulation causes vestibular glands to secrete mucus into vestibule

-mucus lubricates vestibule and vagina to aid intercourse

female orgasm

-clitoris