Reproductive System, Part 1

Interstitial Cells

(Leydig cells) - found between seminiferous tubules, produce and secrete androgens, primarily testosterone, into surrounding interstitial fluid

Sexual Intercourse (what its for, how NS is involved, what is an erection)

(copulation, or coitus) is mechanism that optimizes chances of fertilization. Erection (parasympathetic NS) and ejaculation (sympathetic NS) are basic phases of male sexual response Erection - enlargement and stiffening of penis caused by engorgement of blood; allows penis to enter vagina

Diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number Pairs = homologous chromosomes

Sustentacular cells (what they surround, 3 things they provide in terms of support)

(nurse cells, Sertoli cells) -surround spermatogenic cells to provide support: 1. Provide structural support for stem cell development and secrete testicular fluid; helps transport sperm in seminiferous tubule 2. Provide nutrients for dividing cells and produce androgen-binding protein (ABP) and inhibin, which help regulate spermatogenesis 3. Phagocytize damaged spermatogenic cells and excess cytoplasm released from maturing spermatids

Meiosis I: Telophase I and Cytokinesis

*After cytokinesis I, two cells will be haploid (only half of chromosomes , 23 chromosomes, each has 2 chromatids that are not identical after crossing over step in meiosis 1).* Nuclear envelopes form around chromosomes, which may temporarily decondense. Spindle disappears. Cytokinesis may divide cell into two.

Meiosis I: Metaphase I and Anaphase I

*Meiosis 1 metaphase equatorial plate is positioning chromosomes such way that 23 chromosomes are pulled in one direction and another 23 are pulled in the opposite direction. Each of those 23 has 2 sister chromatids because of the duplication that took place in S phase of interphase I. The choice what chromosome (mom's or dad's) goes to what pole is random.* As prophase I ends, a spindle forms and attaches to each tetrad. During metaphase I of meiosis, paired homologous chromosomes line up across the center of the cell. As the cell moves into anaphase I, the homologous pairs of chromosomes separate. During anaphase I, spindle fibers pull each homologous chromosome pair toward opposite ends of the cell.

Meiosis I: Prophase I

*homologous chromosomes (one from mom, one from dad) line up next to each other and perform crossing over (homologous recombination). Now mom's and dad's chromosomes are mixed.* The nuclear membrane begins to break down and disintegrate. The replicated chromosomes begin to condense and become visible. Homologous chromosomes synapse (pair up) to form bivalents. Spindle microtubules begin to form.

Corpora Cavernosa

--Corpora cavernosa - paired erectile bodies that split to form crura at base of penis;

Corpus Spongiosum (one)

--Corpus spongiosum (one) expands to form bulb of penis at base; sits between crura where they form root of penis and connect penis to pelvic bones

Semen after ejaculation (5 min, 15-30 min)

-Five minutes post-ejaculation: semen coagulates due to activities of clotting proteins from seminal vesicles and enzymes from prostate; prevents semen from leaking out of female reproductive tract -After 15-30 minutes: semen clot breaks up due to activity of PSA and other anticoagulants from prostate. Sperm cells are gradually released from clot, activated, and begin their ascent up female reproductive tract

Seminal fluid (def and 4 components)

-a yellowish secretion that makes up 60-70% of semen volume; composed of: 1. Fructose - sugar that sperm utilize for ATP synthesis 2. Prostaglandins - stimulate smooth muscle contraction in both gender's reproductive tracts and increase sperm viability 3. Coagulating proteins and enzymes combine to form a temporary clot of semen in female reproductive tract 4. pH of seminal fluid is alkaline to neutralize acids in male urethra and female reproductive tract

Accessory sex glands: *Prostate* (size, location, what it surrounds, what its made up of, what happens during ejaculation)

-egg-sized gland found inferior to urinary bladder; -surrounds urethra and ejaculatory ducts. -Made up of 20-30 tubular glands dispersed among smooth muscle and connective tissue; enclosed in a fibrous capsule. -During ejaculation, prostatic smooth muscle contracts; squeezes prostatic secretions into prostatic urethra via several ducts

Lobules of the testes, seminiferous tubules, rete testis, efferent ductules

-internal segments -contain tightly coiled loops called *seminiferous tubules* where sperm is produced. -Seminiferous tubules of each lobule merge into a single *straight tubule* that moves sperm in rete testis -*Rete testis* - network of tubules in posterior testis, transports sperm to efferent ductules -*Efferent ductules* carry sperm from rete testis to epididymis; first portion of duct system

Testes (location, tissue, and 2 important functions)

-located outside abdominopelvic cavity in a saclike structure composed of skin, smooth muscle, and connective tissue, called scrotum -Testes perform two important functions: sperm production and secretion of androgen hormones, primarily testosterone

Spermiogenesis (what it is, where it occurs, 4 characteristics)

-process of sperm maturation -involves cellular shape and size changes -Begins in testes as spermatids elongate and shed excess cytoplasm 1. An acrosome develops; covers nucleus and helps with fertilization of female gametes 2. Mitochondria increase in numbers and move to developing flagellum site 3. Spermatids separate from sustentacular cells and are released into seminiferous tubule lumen 4. Spermatids develop a head, midpiece, and tail as they mature into sperm cells

Semen (def, amount, pH)

-sticky whitish mixture of sperm (makes up about 5% of semen volume) and all fluids from different anatomical structures sperm traveled through. -Typical ejaculate is 2.5 and 5 ml in volume; contains between 40-750 million sperm cells -Alkaline pH of semen helps to make sperm fully motile and to begin process of capacitation: Process that enables sperm to penetrate and fertilize an immature female gamete

Male Reproductive System consists of? Sperm travels where? Fluid it travels in and what secretes that fluid?

-testes = produce sperm (male gonads inside scrotum -sperm travels through ducts that lead to an opening in penis -accessory glands secrete semen, fluid that accompanies sperm through these tubes or ducts

What is triggered by increased testosterone

1. spermatogenesis 2. appearance of secondary sexual characteristics: -Growth of pubic, axillary, and facial hair -Larynx enlarges and vocal cords thicken, results in a noticeable "Adam's apple" and deepening voice -Skin thickens and sebaceous glands increase secretion

Two cell types found within seminiferous tubules

1. spermatogenic (form sperm 2. sustentacular (support sperm production)

Meiosis

Cell division that *produces reproductive cells* in sexually reproducing organisms daughter cells have *half # of chromosomes* to ensure correct # in gametes and eventually zygote Before it begins, the cell's DNA is replicated so that each new cell will have a complete identical copy of chromosomes (*sister chromatids*) 2 phases: meiosis I and meiosis II, each having prophase, metaphase, anaphase, telophase

Genes

DNA segments that code for specific proteins (make up chromosomes)

alleles

Different forms of a gene

Ejaculation, Emission, Expulsion

Ejaculation - process to expel semen from penis; under sympathetic nervous system control that occurs in two stages: 1. Emission - movement of *sperm*, *testicular fluid*, and *prostate and seminal vesicle secretions* into urethra 2. Expulsion - occurs as semen, sperm, and fluids from other regions of reproductive system *accumulate in urethra* (Motor neurons from spinal cord stimulate rhythmic contraction of skeletal muscles at base of erectile columns of penis; elicits expulsion of semen from urethra)

Homologous Recombination

Exchange of genetic information between homologous DNA molecules. Takes place during prophase of meiosis I

Blood circulation and innervation in penis

Internal iliac arteries provide branches (internal penile arteries); supply blood to penis Sensory and motor fibers from both sympathetic and parasympathetic nervous systems innervate penis; tactile, pressure, and temperature receptors are found in abundance Both are important for sexual stimulation and control of smooth muscles that control distance of scrotum from body wall

Meiosis II

Meiosis II is the division of haploid cells with non-identical (croosed-over) chromatids. After meiosis II the product is 4 haploid cells each having 23 chromosomes that are all different.

Benign Prostatic Hyperplasia and Prostate Cancer

Prostate expands rapidly until about age 30; further enlargement often occurs after age 45; if prostate is noncancerous but expands to point of compressing urethra, condition is called benign prostatic hyperplasia, or BPH Sometimes an enlarged prostate is secondary to prostate cancer; second most common cancer in U.S. men (after non-melanoma skin cancer); one of leading causes of cancer death among men of all races Screening for prostate cancer usually includes a digital rectal examination, in which a medical professional palpates prostate through anterior rectal wall, and assessment of blood prostate-specific antigen (PSA) levels. PSA blood levels below 2.5 ng/ml are considered normal. If PSA levels are over 4.0 ng/ml, tissue biopsy specimens from different sites in prostate are taken to look for cancerous cells

The ducts the sperm travels through are involved in?

Sperm travels through a series of ducts that provide nourishment and support; ducts are involved in ejaculation in which sperm is expelled from penis

Blood and nerve supply of testes (4)

Testicular artery - branch from abdominal aorta; provides testes with arterial blood Venous plexus drains blood from testes into testicular veins Both divisions of autonomic nervous system innervate testes Testes contain a large number of nociceptors and thermoreceptors

Puberty in boys

Testosterone levels increase dramatically at puberty which leads to following changes. Puberty begins in boys between 12 and 14 years of age; hypothalamus increases secretion of GnRH; stimulates activation of HPG axis

What happens during sexual arousal? (NS)

a parasympathetic reflex triggers release of nitric oxide (NO) from blood vessels endothelial cells; relaxes arteriole walls Arterioles dilate in blood sinuses in erectile tissue; allows for a large volume of blood to enter tissue. Increased blood flow and widening blood sinuses causes an erection Corpus spongiosum does not become as rigid as corpora cavernosa; allows sperm and semen to travel through urethra unimpeded

Somatic effects of testosterone (3)

anabolic in nature (bone density, erythrocytes production, behavior changes)

Ductus deferens (where it begins, where it travels and with what, where it ends, its epithelium, what happens during ejaculation, its storage capabilities)

begins at tail of epididymis where ductus epididymis widens travels with testicular arteries, veins, and nerves through a fibrous tunnel (inguinal canal) into pelvic cavity. Loops around ureter and passes over lateral side and down posterior surface of urinary bladder Terminates in a saclike structure called ampulla Mucosa of this hollow tube consists of pseudostratified epithelium and three layers of smooth muscle, called muscularis. During ejaculation, smooth muscle contracts; squeezes sperm forward along tract. Ductus deferens can store sperm for months and reabsorb any sperm that has not been ejaculated over time

Penis main function (+internal penis and external penis)

delivers sperm into female reproductive tract *External penis* has three parts: root, body, and glans penis (where external urethral orifice is located). Loose skin of penis forms a circular fold called prepuce, or foreskin; portion removed by circumcision *Internal penis* - includes three cylindrical erectile bodies. Each erectile body is a spongy network of connective tissue and smooth muscle with vascular spaces

Zygote and what it must have

divides to produce all the cells of a NEW HUMAN! Must have correct # of chromosomes (half from ovum and half from sperm) = 46 chromosome (23 pairs)

When do germ cells start meiosis I in girls?

during prenatal development and freeze at the prophase I of meiosis I until puberty.

Accessory sex glands: *Seminal Vesicles* (def, where ducts converge and what they form, histology)

exocrine glands near ampullae of ductus deferens duct of each seminal vesicle converges with ductus deferens to form ejaculatory ducts Mucosa layer is made up of pseudostratified columnar epithelium that secretes seminal fluid

Accessory sex glands of the male reproductive system are (def, not examples)

exocrine glands that produce liquid portion of semen

Epididymis

filled with ductules site of sperm maturation and storage. Includes a head, body, and tail region. Sperm moves from head to narrow body, then on to small inferior tail .

Testosterone (4)

hormone: -stimulates and regulates spermatogenesis -male reproductive physiology -regulated by multi-tiered negative feedback loop -development of male characteristics

Primary spermatocyte

is pushed toward lumen of seminiferous tubule and undergoes first meiotic division forming two smaller haploid (1n) cells that remain connected, called secondary spermatocytes

ductus epididymis (histology, length)

long, coiled tube lined with pseudostratified epithelial cells; display nonmotive microvilli called stereocilia. Microvilli absorb excess testicular fluid, provide nutrients to sperm, and complete maturation process of sperm Length of ductus epididymis allows sperm to be stored for months until they are ejaculated or reabsorbed

Prostatic Secretions

make up 20-30% of semen volume; milky fluid that contains: 1. Citrate - another sugar that sperm can utilize for ATP synthesis 2. Prostate specific antigen (PSA) and other enzymes - dissolve semen clot in female reproductive tract to allow sperm to proceed further into tract 3. Antimicrobial chemicals - inhibit some bacterial growth to decrease risk of infection in female reproductive system 4. pH is alkaline to neutralize acids in urethra and female reproductive tract

Accessory sex glands: *Bulbourethral glands (Cowper's glands)* (size, location, features, secretions)

marble-sized paired glands found at base of penis on either side of membranous urethra Each gland has a short duct that connects it to urethra Secrete a thick, alkaline mucus-like fluid that helps neutralize acidic urine remaining in urethra in response to sexual stimulation Also lubricate glans penis during intercourse

Myoid Cells

muscle-like cells that surround seminiferous tubules, contract to push sperm and testicular fluid through tubules

Spermatogenesis (definition, what regulates it, when it begins, where it occurs)

process in which male gametes, or sperm cells, develop; regulated by hormones from hypothalamus and anterior pituitary glands. Begins at puberty and continues for duration of lifespan. Occurs in seminiferous tubules by sperm-forming (spermatogenic) cells

Fertilization

process of sperm and egg fusing to form a zygote (cell)

Secondary spermatocytes

progress through second meiotic division. Newly formed, are four small and round haploid spermatids that continue to move toward lumen of tubule

The reproductive system is in a state of hibernation until..

puberty where reproductive organs mature and become functional

Hypothalamic-pituitary-gonadal (HPG) axis and its tiers

regulates hormones involved in testosterone production and testicular function First-tier control - Gonadotropin-releasing hormone (GnRH), secreted by hypothalamus Second-tier control - anterior pituitary detects GnRH; stimulates secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Third-tier control - in testes: -LH stimulates interstitial cells to produce testosterone -FSH stimulates sustentacular cells to secrete androgen-binding protein (keeps testosterone in vicinity of spermatogenic cells) and inhibin hormone -Inhibin decreases release of FSH; testosterone reduces GnRH secretion (negative feed-back)

Urethra + types

reproductive and urinary sys organ in males it transports both urine and semen Types: 1. Prostatic urethra is surrounded by prostate gland 2. Membranous urethra passes through external urethral sphincter 3. Spongy urethra extends through penis and terminates at external urethral orifice

Ejaculatory Duct (length, where it receives sperm, where it travels)

short duct receives sperm from ductus deferens' ampulla where an accessory organ called seminal vesicle is located. Duct travels through another accessory gland (prostate) on its way to its destination (urethra)

Spermatogonia

stem cells that initiate spermatogenesis; 46 chromosomes (diploid, 2n); After puberty, spermatogonia become fully functional stem cells that divide by mitosis allowing one daughter cell to remain a stem cell while other becomes a diploid primary spermatocyte

Orgasm, Resolution, Refractory Period

time period during which feelings of pleasure are experienced; coincides with ejaculation Resolution, or relaxation, follows orgasm and ejaculation; blood vessels in erectile tissue and blood sinuses constrict, forcing blood out of penis A refractory period, or latent period, occurs after ejaculation that varies in duration, where a man cannot achieve another orgasm

When do germ cells start meiosis I in boys?

when puberty starts with the increase of gonadotropin-releasing hormone.