reproductive system - male

largest and smallest cell in the body

largest - egg

smallest - sperm

fetal development, when does external genitals develop?

external genitals begins around 12 weeks

when do nipples form?

early fetal development (7 weeks)

before the formation of specific male or female sex organs @ 12 weeks (why you need to wait until 2nd trimester for gender reveal)

how is biological sex determined?

biological sex determined from your genes

23 pairs of chromosomes, 46 total (23 from mom, 23 from dad!)

genes encode for protein with specific function (DNA → RNA → Protein)

• 23rd pair is referred to sex chromosomes

  • XX - female

• XY - male

X chromosome versus Y

• X chromosome has about 900 genes

• Y chromosome has 50

SRY gene (sex-determining region of Y protein)

Provides instructions for making a protein called the sex-determining region Y protein

• SRY protein functions as a transcription factor (it alters transcription, turns genes on or off); alters gene expression on specific tissues at specific times resulting in development of male sex organs

• turns ON testes promoting genes

• turns OFF ovary-promoting genes

Label the anatomy of the male reproductive system *add photo

Label the anatomy of the female reproductive system *add photo

Development of external reproductive structures to FEMALE

• We begin undifferentiated (not male or female) with genital tubercle, genital fold, genital swelling

• we form glands which turn into clitoris

• genital folds form labia minora

• genital swelling on lateral side forms labia majora

Development of external reproductive system for MALES

• WITH SRY gene present

• We begin undifferentiated (not male or female) with genital tubercle, genital fold, genital swelling

• igenital tubercle → glans penis

• medial genital folds → shaft

• genital swelling → scrotum

Development of internal reproductive structures - FEMALE

• Begin undifferentiated with two sets of tubes (Wolfian ducts and Mullerian ducts) which can differentiate into either testes or ovaries

• No SRY present (XX, female)

• Wolfian ducts degrade

• Mullerian ducts form uterine tubes and uterus

• Biological (CHECK SPELLINGGG) gonads become ovaries

Development of internal reproductive structures - MALE

• Begin undifferentiated with two sets of tubes (Wolfian ducts and Mullerian ducts) which can differentiate into either testes or ovaries

• SRY present (XY, male)

• Mullerian ducts degrade

• Wolfian ducts form epididymis and vas defrens

• Biological (CHECK SPELLINGG) gonads form testes

What happens if XY but SRY gene is mutated?

Swyer syndrome - disorder of sex development (XY gonadal dysgenesis)

• appear normal and healthy w/ external female genitals but internal structures are unlike typical males or females (cryptorchidism)

• Stella Walsh - Polish olympic gold medalist who was robbed and shot and only the autopsy revealed she had Swyer syndrome

Symptoms of Swyer syndrome

• breasts fail to develop

• no menstruation (no egg released)

• no pubic or axillary hair

Treatment of Swyer syndrome

• hormone replacement (estrogen & testosterone)

• removal of cryptic internal organs due to cancer risk

Why are people with Swyer syndrome treated with female hormones?

Testosterone is the precursor to estrogen

aromatase is the converting enzyme (testosterone → estrogen)

functions of male reproductive system

1. Produces androgens (sex hormones), such as testosterone (females also have it but like 1/8th)

2. Reproduction through the formation of sperm (spermatogenesis) (sperm are homologous to the ovum [egg])

3. Delivery of sperm during sexual intercourse

Structures

Scrotum - big sac with testes, epididymis, ductus (vas) deferens

Glands - prostate, seminal, bulbo-urethal (mature the sperm I think)

Penis - shaft/body, head/gland, prepuce/foreskin, external urethral orifice

sperm versus semen

sperm - single cell (half of genetic information)

semen - the glands produce secretions that help the sperm swim, act as energy, and degrade obstacles in the way to get home like nemo

seminal gland function

prostate gland function

bulbo-utethal gland function

prostate cancer

• 2nd most conmon cancer in men (second to skin cancer)

• 1/8 men diagnosed, 1/41 die

• over age 65 highest risk, under 40 rare (reccomended to start getting prostate exams @ age 40 through palpating the prostate through the rectum, if family history younger)

• Blood tests- test for PSA (Prostate-specific antigen); poor predictor because PSA levels fluctuate

  • suspicious levels result in biopsy

  • depending on stage, chemotherapy or surgical removal treatment

• EARLY DETECTION SAVES LIVES

Anatomy of testes

• external tunica albunginea - encloses/houses the seminiferous tubules

• repeated _________

• Within the tubules are 5 types of developing sperm cells called germ cells + supporting sertoil cells

• Sperm develop superficial to deep

Sertoli cells

support and protect germ cells, and form the blood-testis barrier

also called “nurse” cells for their supportive role

5 stages of germ cells development

1. spermatogonia( 2n)

2. primary spermatocyte (2n)

3. secondary spermatocyte (2n)

4. spermatid (n)

5. sperm (n)

2n is 23 pairs of chromosomes, n is 23 individual chromosomes

spermatogonia

Structure of sperm

Head contains DNA, mid-piece mitochondria, tail provides motility

Acrosome - head that carries DNA

Mitochondria give tail (flagellum) energy to swimmmmmm

Gametogenesis - similarities between men and women

• both haploid

Gematogenesis - differences male versus women

what cells produce testosterone?

leydig cells

• located outside the seminiferous tubules and produce the steroid hormone testosterone

• begins around week 7 of pregnancy, contributes to development of male structures

• produce approx. 6 to 7 mg testosterone/day

functions of testosterone

• increased libido

• increased muscle mass

• body hair

• bone strenghtening

• sperm production

• voice change

• penile development

• development of

Control of Testosterone feedback loop

Hypothalamus → GnRH (gonadotropin-releasing hormone)

Goes to anterior potuitary

Anterior pituitary → LH (lutenizing hormone) and FSH (folllicle stimulating hormone)

LH goes to laydig cells that produce testosterone

• built in negative feedback loop _______

FSH goes to sertoli cells, releases inhibin