male reproductive system

sex cell

sex cell

unlike a somatic cell, it contains 1/2 the amount of chromosomes and different genetic material (due to recombination)

male gamete production

half a billion sperm per day in comparison to one oocyte per month in females

testes

male gonads that

• secrete male sex hormones (androgens)

• produce male gametes (sperm)

pathway of sperm

testis → epididymis → ductus deferens → ejaculatory duct → urethra

seminal glands, prostate, bulbo-urethral glands

accessory glands that secrete fluids into the duct system for semen production

spermatic cord

between abdomen and testes that begins at inguinal canal down to scrotum

enclose blood vessels, nerves, lymphatic vessels of testes

dartos muscle

layer of smooth muscle in dermis of scrotum

cremaster

layer of skeletal muscle deep to dermis

tenses scrotum and pulls testes closer to body during sexual arousal or decreased temps

seminiferous tubules

location of sperm production and connect to rete testis

Leydig cells and germ cells

Leydig cells

produce testosterone

germ cells

arise into the future sperm cells and live in wall of seminiferous tubules

immobile sperm

produced by the testes and not yet capable of fertilizing an oocyte

moved by cilia lining efferent duct into the epididymis

epididymis tail

stores sperm

ductus deferens

smooth muscle → peristaltic contractions propel sperm and fluid

can store sperm for several months

male urethra

used by urinary and reproductive systems

urethral regions

• prostatic (through prostate)

• membranous

• spongy

accessory glands

produce fluid component of semen

mixture of secretions, each with distinctive biochemical characteristics

accessory gland functions

• activate sperm

• provide nutrients sperm need for motility

• propel sperm and fluids along reproductive tract mainly by peristaltic contractions

• produce buffers to counteract acidity of urethral/vaginal environments

ejaculatory duct

short passageway that starts at junction of ampulla of ductus deferens and duct of seminal gland

penetrates prostate wall and empties into prostatic urethra, letting fluid out of seminal gland into urethra

semen

contains sperm and seminal fluid

seminal fluid

composed of

• fructose (nutrients for sperm)

• alkaline (neutralize vaginal canal)

pubic symphysis

joint, superior to root of penis

corpora cavernosa and corpus spongiosum

two types of erectile tissue → blood goes through here during an erection

mitosis

somatic cell division that produces two diploid (2n) daughter cells

identical numbers and pairs of chromosomes, each pair being homologous chromosomes

meiosis

gamete cell division that produces 4 haploid (n) gametes, each with 23 individual chromosomes

1 spermatogonia → 4 sperm

zygote

formed by the fusion of a male and female gamete = 46 chromosomes

meiosis I

homologous chromosomes separate

meiosis II

sister chromatids separate

crossing over

exchange of genetic material that increases genetic variation among offspring

occurs in meiosis I

spermatogenesis

process of sperm production that begins at puberty and continues past age 70

complete process takes ~64 days

spermatogenesis steps

1. mitosis (of initial stem cell)

2. meiosis

3. spermiogenesis (maturation)

spermatogenesis pathway

one primary spermatogonium → 2 primary spermatocyte → meiosis I → secondary spermatocyte → meiosis II → 4 spermatid → spermiogenesis → sperm → enter ST lumen → spermiation

spermatogonium

stem cell in seminiferous tubule walls, doesn't move but constantly regenerate

primary spermatocyte

one cell undergoes rest of spermatogenesis, goes onto complete meiosis I to produce secondary spermatocytes

other cell will replace itself

spermiogenesis

maturation of spermatids into sperm through major structural changes

seminiferous tubules contents

from basal layer to lumen:

spermatogonia → spermatocytes at various stages of meiosis → spermatids → sperm

and large nurse cells

nurse cells

take care of sperm, give them nutrients and tell them to divide during spermatogenesis

spermiation

sperm loses attachment to nurse cell and enters lumen of seminiferous tubule

acrosome

a vesicle at the tip of a sperm cell that contains enzyme to dissolve egg wall so the sperm can enter

nurse cell functions

• maintenance of blood testis barrier

• support mitosis and meiosis

• support spermiogenesis

• secretion of inhibin

• secretion of androgen-binding protein

capacitation

change that sperm go through to become motile and fully functional

capacitation steps

1. sperm become motile

2. sperm become capable of fertilization

sperm anatomy

• head

• neck

• middle piece

• tail

mitochondrial spiral

contains a lot of mitochondria in this section of sperm to make ATP to power the tail

testosterone effects

• stimulates spermatogenesis

• maintains libido

• stimulates bone and muscle growth

• establishes and maintains male secondary sex characteristics

• maintain accessory glands and organs of male reproductive system