Nat Sci 179 Lecture Notes Chapter 27 Male Reproductive System

Front 1

Sex Cells

Back 1

gametes, sperm or egg
-have 23 chromosomes in humans
-when sperm fertilizes egg, zygote has 46 chromosomes

Front 2

male karyotype is 46XY; female is 46XX

Back 2

-sex of baby is determined by father’s sperm
-all eggs have one X, but sperm may have an X or a Y

Front 3

Y chromosome

Back 3

as SRY gene (sex-determining region of Y)
-codes for protein TDF (testis-determining factor)
-TDF protein affects other genes on other chromosomes, including the X chromosome
-results in some cells having androgen receptors
-also results in starting differentiation of male gonads

Front 4

by 9 weeks a male fetus

Back 4

has immature testes that start producing testosterone

Front 5

male development requires

Back 5

testosterone & androgen receptorsfemale development results from

Front 6

female development results from

Back 6

lack of testosterone at this stage, not from estrogen as we might think

Front 7

through the 5th to 6th week of development

Back 7

male and female embryos are indifferent

Front 8

by 7th to 8th week

Back 8

differentiation has begun

Front 9

all embryo start with

Back 9

1-genital tubercle

2-urogenital folds

3-labioscrotal folds

Front 10

genital tubercle

Back 10

becomes penis in male, clitoris in female

Front 11

urogenital folds posterior to the genital tubercle

Back 11

-in male, fuse to enclose the urethra within penis
-in female, become labia minora, small folds around vaginal opening
-note that in female, the urethra stays separate from the clitoris

Front 12

labioscrotal folds, lateral to urogenital folds

Back 12

-in male, fuse to become scrotum which will later hold the testes
-in female, becomes labia majora, more external folds around vaginal opening
-note that male and female parts are homologous

Front 13

Male & female developmental similarities

Back 13

-there is an equivalent part in both sexes, although they develop differently
-male tract develops from mesonephric duct
-female tract develops from paramesonephric duct
-the undeveloped duct in each sex degenerates

Front 14

testes begin development

Back 14

testes begin development up near the kidneys

Front 15

during development the gubernaculum

Back 15

a cord between testis & floor of pelvic cavity
-shortens & guides the testis down through an opening called the inguinal canal
-normally starts in 6th-10th week, testes reach scrotum by 28th week

Front 16

the tunica vaginalis, a pouch of tissue

Back 16

follows the testis down to the scrotum
-later covers part of the testis, and closes at the top
-this is not in text:
-in about 25% of males the tunica vaginalis does not close
-may lead to an inguinal hernia: loop of intestine can move into the space, pushed by abdominal pressure
-if becomes strangulated hernia, strangulated tissues may die

Front 17

cryptorchidism is condition of boy born with undescended testes (one or both)

Back 17

-can lead to infertility if not corrected because sperm require 35 degrees C to be healthy.
-often descend during first year after birth
-if not, usually easily corrected with hormones or surgery

Front 18

-testes

Back 18

male gonads; site of sperm production
-seminiferous tubules
-located inside testes
-location of sperm cell production

Front 19

scrotum

Back 19

sac that holds the testis; maintains 35 dg C

Front 20

epididymis

Back 20

-lies on posterior side of testis
-site of sperm maturation & storage

Front 21

ductus (vas) deferens

Back 21

-duct that sends sperm out of epididymis
-widens into the ampulla behind the bladder
-joins with duct of the seminal vesicle to form the ejaculatory duct
-ejac. duct passes through the prostate gland, then to the urethra

Front 22

accessory glands

Back 22

-seminal vesicles, prostate gland, bulbourethral gland
-secrete components of semen
-1st two needed for health of sperm, food source, survival of sperm in vaginal environment
-bulbo. secretion lubricates tip of penis during sexual arousal

Front 23

prostate gland

Back 23

-tends to grow with age, can put pressure on urethra
-causes urge to urinate, need to urinate at night, even bladder & kidney infection
-second most common cancer in men (after lung)
-numbers similar to incidence of breast cancer in women (around 9-12%)

Front 24

PSA

Back 24

(prostate specific antigen) test has been highly questioned and is used less than previously

Front 25

penis

Back 25

-transfers sperm to female vagina
-also holds urethra for exit of urine
-both fluids cannot pass out at same time

Front 26

prepuce = foreskin

Back 26

-loose fold of skin that covers distal part of penis
-often removed at birth in circumcision
-question as to whether there are health risks to leaving it intact

Front 27

corpus spongiosum and corpus cavernosum

Back 27

erectile tissues
-fill with blood to produce an erection
-these tissues are affected by viagra