Reproductive System

Spermatogenesis product

4 functional gametes

When does spermatogenesis begin?

at puberty and continues throughout the lifespan

Where does spermatogenesis occur?

in the seminiferous tubules

Stages of spermatogenesis

mitosis
meiosis
spermiogenesis

stages of spermatogonia to sperm

mitosis of the spermatogonium --> type A and B
meiosis of the spermatogonium type B cell --> primary spermatocyte --> meiosis 1 --> secondary spermatocyte --> meiosis 2--> spermatid --> anatomically mature sperm

spermatogonia

stem cell that divides and builds up the basal lamina line; beginning at puberty the mitosis results in a type a and type b cell (due to surge in FSH)

Type A Spermatogonia

continues mitosis to maintain epithelial basal lamina

Type B Spermatogonia

cells that move towards lumen and develop into primary spermatocytes

spermatid

small, non-motile cells close to lumen of tubule
**NOT yet anatomically mature sperm

What happens during spermiogenesis?

spermatids elongate, shed excess cytoplasm, and form a tail

Oogenesis

product is one functional gamete and three polar bodies

When does oogenesis occur?

Begins in fetal life and ends at menopause

Stages of Oogenesis

oogonium enters mitosis and divides into a primary oocyte is arrested in prophase 1 until puberty --> primary oocyte with spindle --> meiosis 1 (in response to LH surge) --> polar body and secondary oocyte produced --> ovulation and fertilization of secondary oocyte -->meiosis 2--> ovum and 1 polar body
polar body undergoes meiosis 2 and produces 2 polar bodies

What does HPG axis stand for

hypothalamic pituitary gonadal axis

HPG axis in females

The hypothalamus stimulates the release of gonadotropin releasing hormone which stimulates the anterior pituitary to release LH and FSH which stimulates the ovaries to release estrogen and progesterone

HPG axis in males

The hypothalamus stimulates the release of gonadotropin releasing hormone which stimulates the anterior pituitary to release LH and FSH. FSH initiates spermatogenesis and LH stimulates interstitial cells to release testosterone, the final trigger for spermatogenesis. Inhibin helps regulate hpg when there is too high levels of certain hormones.

What hormones control the ovarian cycle?

FSH and LH

What hormones control the uterine cycle?

Estrogen and Progesterone

Gonadotropic-releasing hormone

comes from the hypothalamus
targets anterior pituitary
inhibited by inhibin

Follicle Stimulating Hormone

secreted from anterior pituitary
targets the gonads
testis: stimulates production of androgen binding protein which is necessary for sperm maturation
ovary: stimulates maturation of ova every 28 days

Luteinizing Hormone

secreted from anterior pituitary
targets the gonads
testis: targets interstitial cells to release testosterone
ovary: triggers ovulation

Estrogen

secreted by the ovaries, corpus luteum and follicular cells
targets uterus and promotes the proliferative phase of the uterine cycle, secondary sex characteristics

progesterone

secreted by corpus luteum
targets uterus and prepares and maintains endometrium for implantation

Ovarian Cycle

monthly series of events associated with maturation of ovum
result: ovulation of a single secondary oocyte arrested in meiosis 2
FSH and LH control the cycle

phases of ovarian cycle

follicular phase
luteal phase
*separated by ovulation

Follicular Phase

pre-ovulatory; period of follicle growth (days 1-14)...dominant follicle selected; estrogen begins to be secreted

Luteal Phase

post-ovulatory
period of corpus luteum activity (days 14-28)
estrogen and progesterone* secreted

Uterine Cycle

cyclic changes in endometrium in response to ovarian hormones

Uterine Cycle Phases

Menstrual Phase, Proliferative Phase, Secretory Phase

Menstrual Phase

day 1-5; Functional layer of the endometrium is shed

Proliferative phase

days 6-14; functional layer of the endometrium is rebuilt

secretory phase

days 15-28; begins immediately after ovulation; enrichment of the blood supply and glandular secretion of nutrients prepare endometrium to receive an embryo

where do the sperm become anatomically mature?

seminiferous tubules

where do sperm become functionally mature

epididymis

pathway of sperm

seminiferous tubules --> straight tubule --> rete testis --> efferent ductules --> epididymis --> ductus deferens --> ejaculatory duct --> urethra

site of fertilization

ampulla; widest portion, forms most of the uterine tube

four regions of the uterine tube

infundibulum, fimbriae, ampulla, isthmus

site of implantation of embryo

uterine lining

uterine wall layers

perimetrium, myometrium and the endometrium

Endometrium

mucosal lining of the uterus; if fertilization occurs, sit of embryo implantation and development

Myometrium

layers of smooth muscle; bulk of the wall that contracts rhythmically; responsible for labor and delivery

perimetrium

serous layer (visceral peritoneum)

Why can fertilization occur outside of the female reproductive tract?

The fimbriae and the ovary are not 100% connected so sometimes the ovum can be ovulated into the pelvic cavity and the sperm can also end up in the pelvic cavity

sperm's journey to meet the egg

male urethra-->vagina--> uterus --> fallopian tube

Semen

sperm + liquid fluid

What produces the viscous volume of semen?

seminal vesicles

True or False?Liquid provides a transport medium and nutrients (e.g. fructose) for the sperm and contains chemicals that protect, activate, and facilitate the movement (e.g. relaxin) of the sperm

True

Fructose provides what for semen?

nutrients for the sperm for ATP production

Role of Prostaglandins in the sperm

decrease viscosity of mucus in cervix, stimulates reverse peristalsis in uterus (PROMOTES pregnancy)

Fibrinogen in semen; Fibrinolysis?

Fibrinogen coagulates semen post ejactulation; fibrinolysin liquefies it

Alkalinity of semen helps do what?

neutralizes acid in male urethra and female vagina in order to protect the sperm and enhance its motility

Sperm regions

Head, Midpiece, Tail

Head of sperm

contains genetic material; nucleus of DNA and helmetlike acrosome contains hydrolytic enzymes that enable the sperm to penetrate an egg

Midpiece of Sperm

metabolic region with lots of mitochondria that produce ATP to power tail and movement

Tail of sperm

locomotor region; flagellum

Role of Sustentocytes/Sertoli cells

these cells surround developing cells in order to provide nutrients and signals to dividing cells; move cells along to lumen; secrete testicular fluid into lumen for sperm transport; phagocytize germs; tight junctions form blood testis barrier!

Blood Testis Barrier

a physical barrier between the blood vessels and the seminiferous tubules of the testes; created by Sertoli cells

Role of male reproductive system

produce sperm & introduce it into the female body

Role of female reproductive system

produce ova, receive sperm and provide for union of the gametes, harbor an embryo and give birth, nourish offspring

Gonads

Testes and Ovaries

Exocrine function of gonads

produce gametes

Endocrine function of gonads

secrete steroid sex hormones
males: androgens
females: estrogens and progesterone

Accessory Glands in males

produce materials that support the sperm (liquid part of semen)

Accessory Glands in females

provide lubrication for intercourse

Role of Inhibin

released from gonads of male or female and exerts a negative feedback loop on FSH release from the anterior pituitary

System of ducts in males

epididymis-->ductus deferens-->ejaculatory duct--> urethra
**sperm delivered to exterior through this

accessory sex glands in males

seminal vesicle, prostate gland and bulbo-urethral glands

Scrotum

sac of skin that hands outside of the abdominopelvic cavity that contains paired testes @ 3 degrees Celsius lower than core body temp due to necessary sperm production

Dartos Fascia

smooth muscle that when contracted it wrinkles the scrotal skin in order to decrease available surface area. the thickness increases to reduce heat loss

Cremaster Muscles

bands of skeletal muscle that contract to elevate the testes and pull them closer to the body to reduce heat loss
**cremaster reflex

testes tunics

tunica vaginalis (outer)
tunica albuginea (inner, fibrous capsule)

True/False: when sperm leave the testes they are anatomically mature but are NOT functionally mature

true- they anatomically become mature in the seminiferous tubules and become functionally mature in the epididymis

Blood Supply in Male Reproductive System

testicular arteries from abdominal aorta, testicular veins arise from pampiniform venous plexus surrounding each testicular artery

Spermatic Cord

encloses nerve fibers, blood vessels and lymphatics that supply testes & ductus deferens

Seminiferous Tubules

site of sperm production; spermatogenic cells embedded in sustentocytes

Myoid Cells

squeeze sperm and testicular fluid out of testes

Interstitial Cells

produce testosterone; surround seminiferous tubules

Penis

Root (internal) and body/shaft (external) that ends in enlarged tip glans penis
Prepuce, or foreskin—the cuff of loose skin covering the glans

Corpus Spongiosum

erectile tissue that surrounds the urethra and expands distally to form gland and proximally to form bulb

Corpus Cavernosa

erectile tissue; (2) paired dorsal; proximal ends from crus of penis

Erection

erectile tissue fills with blood --> penis becomes enlarged and rigid

Epididymis

Highly coiled duct where sperm are stored until ejaculation, **WHERE SPERM BECOME FUNCTIONALLY MATURE--> Become motile**

How do sperm become functionally mature in the epididymis

microvilli absorb testicular fluid and pass nutrients to stored sperm

What happens at the ejaculatory duct?

sperm and seminal fluid are mixed to form semen; duct of seminal vesicle and ductus deferens join to form this duct

Urethra

three regions that serve both urinary and reproductive purpose; prostatic, membranous and spongy urethra

Prostate gland

secretes milky, viscous and slightly acidic fluid;
contains citric acid, fibrinogen and fibrinolysin; plays a role in activation of sperm; enters prostatic urethra via several ducts during ejaculation

Bulbourethral Glands (2)

pea sized; prior to ejaculation, they produce thick and clear, alkaline mucus = pre ejaculatory fluid that lubricates the spongy urethra to facilitate passing of sperm and to neutralize acidic urine traces of urethra.

Male infertility

Ejaculation

semen becomes sticky (fibrinogen)
entangles sperm, sticks semen to vaginal and cervical surfaces, prevents semen from draining out of vagina
**after 20-30 min: semen liquifies and sperm become active, prostaglandins help to thin cervical mucus plug and stimulate uterine contractions to help sperm into uterine cavity

2 requirements for sperm motility

vaginal ph brought to 7.5 (from 3.5-4)
fructose and other sugars provide substrate for sperm ATP production

Meiosis Review

most body cells diploid and contain 23 pairs of homologous chromosones but gametes are haploid and only contain 23 chromosomes

Spermatogenic Cells

give rise to sperm...in the seminiferous tubule walls, the various cell layers tell the stage of spermatogenesis that they are in

Testosterone Effects

In embryos, masculinizes the brain
Prompts spermatogenesis
Has multiple anabolic effects throughout the body
Targets all accessory reproductive organs
Is the basis of the sex drive (libido) in males

Male Secondary Sex Characteristics

pubic, facial hair; enhanced growth of chest and deepening of the voice, skin thickens and becomes oily, bones increase in density and skeletal muscles increase in size and mass

Sexual Response Stages

Erection, Lubrication, Orgasm, Resolution

Male excitement

consists of erection and bulbourethral gland lubrication

Female excitement

vaginal transudate, lubrication from vestibular glands, orgasmic platform formed and tenting effect

what happens during male orgasm (2 e's)

emission and ejaculation

male resolution of the sexual response

detumescence, refractory period

Parasympathetic role in sexual responses

excitement