Ch17: Gonadal (Testes)

Testes

• Paired, ovoid organ

• production of sperm and reproductive steroid hormones

• Secretes testosterone

embryonic stage

Aids in development and differentiation of the primordial gonads

after puberty

stage where testes Helps with sperm production and maintains 2° sexual characteristics

Week 6

Primordial germ cells migrate to gonadal ridges

Surrounded by sex cords to form primitive, bipotential gonads (in both XX and XY)

Sex-determining Region Y Gene

Gene on short arm of Y chromosome is the designated Testis determined factor (TDF) acts as a switch turning to male development pathway

Testis determined factor

Produces a DNA-binding protein that initiates male development

true

true or false: If no Y chromosome (46, XX), female development (ovaries) is followed automatically 

SEMINIFEROUS TUBULES

Contains  germ cells that develop into sperm (spermatogonia) & Sertoli cells

Tubuli recti>Ductuli efferentes testes>Epididymis>Vas deferens

Week 7

Medullary tissues are formed by how many weeks of gestation?

Vitamin C, fructose

Secretory products sperm mixes with as it travels through tubules

leydig cell

Cells that synthesize testosterone

• Its activity is regulated by Luteinizing Hormone from pituitary gland

Luteinizing hormone

ANTI-MULLERIAN HORMONE

Causes mullerian ducts to disappear

Spermatogenesis

Sperm are from spermatogonia

Spermatogonia/Spermatogenesis

undergo mitosis and meiosis to form mature sperm

Spermatogonia>Mitosis>1st spermatocyte>Meiosis 1> 2nd Spermatocyte> Meiosis II>Spermatid

sequence of spermatogenesis

Acrosome, sperm head, nucleus, centriole, neck, mitochondri, midpriece, axoneme, principal piece, tail

identify major parts of sperm

Follicle stimulating hormone, Luteinizing hormone

2 pituitary hormone supporting male fertility

Follicle Stimulating Hormone

1st pituitary hormone acting on sertoli cells to support spermatogenesis

• Acts on germ cells

• Spermatogenesis

Luteinizing Hormone

2nd pituitary hormone acting on testes

Acts on leydig cells to stimulate testosterone synthesis

Testosterone

Principal androgen hormone (male) secreted in response to LH

➢ 2-3% Free

➢ 50% albumin bound

➢ 45% SHBG bound

➢ Provide (negative) feedback control to the hypothalamus and pituitary

8 AM

Peak of testosterone according to PPT

6 AM

Peak of testosterone according to Book bishop cc2

12 AM

Nadir of testosterone according to Book bishop cc2

8 PM

Nadir of testosterone according to PPT

4-10 mg

How much testosterone is secreted daily after puberty?

t

t/f: Testosterone is produced in small amounts by the ovaries and adrenal glands

Estradiol, Dihydrotestosterone

Testosterone is converted to two active metabolites called

Scrotal skin

it is rich in 5α-reductase which converts testosterone to DHT

no virilization

identify this stage

stage 1

identify this stage

stage 2

identify this stage

stage 3

identify stage

stage 4

identify stage

stage 5

identify which stage

Hypothalamic-hypophyseal vascular connections

○ Responsible for LH release by GnRH

○ Becomes functional by weeks 11–12 or 3 weeks after Leydig cells start producing testosterone

postnatal development

a. Development of secondary sex hair (face, chest, axilla

and pubis)

b. Enhanced linear skeletal growth

c. Increase upper body musculature

d. Development of larynx and vocal cords

e. Deepening of the voice

Hypogonadism

leads to imprecise closure of growth plates leading to:

1. Excessive height

2. Long limbs

3. Disproportionate upper and lower body segment

Sertoli Cell

produce mullerian regression factor that aids in regression of female primordial genital tract

Scrotal skin

Rich in is 5α-reductase which converts testosterone to dihydrotestosterone

5α-reductase

converts testosterone to dihydrotestosterone

Tanner staging

Used to diagnose premature or delayed sexual development

Prepubertal, Enlargement of scrotum, increased length of penis, enlargement of testes with growth of glands, mature genitalia

Enumerate stages of genital development

Hypergonadotropic hypogonadism

Hypogonadotropic hypogonadism

Klinefelter’s syndrome

HYPERGONADOTROPIC HYPOGONADISM 

Trisomy (47, XXY)

• Small testicles, gynecomastia,

• azoospermia/sterile/infertility

• ↑ aromatase, ↑ estrogen;

• Reduced bone density and breast

• cancer

• *high risk of osteoporosis 

• increased breast cancer risk

TESTICULAR FEMINIZATION SYNDROME

Complete Androgen Inensitivity Syndrome (CAIS)

Lack of testosterone action

Female phenotype

• May appear to have fully developed breast, female-like distribution off fat & hair

Androgen Insensitivity Syndrome

most severe form of androgen resistance

mutation in androgen receptor gene

may be complete (CAIS) or partial (PAIS)

Quigley scale

Phenoypic grading from “fully masulinized” & “fully feminized” genitalia

5a-Reductase Deficiency

HYPERGONADOTROPIC HYPOGONADISM

● ↓ Testosterone

○ Reduced conversion of testosterone → DHT

● Female phenotype until puberty

● Late action of testosterone

● Mutation in encoding type 2 isoenzyme, maps to chromosome 2p23

MYOTONIC DYSTROPHY

HYPERGONADOTROPIC HYPOGONADISM

● Autosomal dominant

● Genetic disorder that causes progressive muscle loss

and weakness

● Testicular failure (in the 4th decade of life)

Type 1

Myotonic dystrophy with DMPK gene mutation

Type 2

Myotonic dystrophy with CNBP gene mutation

true

true or false: testicular failure usually occurs when px is 20-30s

TESTICULAR INJURY & INFECTION

HYPERGONADOTROPIC HYPOGONADISM

Postpubertal mumps can result in mumps orchitis and permanent testicular injury

SERTOLI CELL ONLY SYNDROME

Also known as germ cell aplasia and arises from Y chromosome microdeletion on Yq11 locus

HYPERGONADOTROPIC HYPOGONADISM

● Normal testosterone action

● Lack of germ cells

● Azoospermia

KALLMANN’S SYNDROME

●X-linked congenital disorder

● Affects the development of the hypothalamus (↓ GnRH)

and olfactory nerves.

● Anosomia

● Hypogonadism during puberty

• hypogonadotropic hypogonadism

Anosomia

 inability to smell and midline defects (cleft palate) color blindness and deafness

● Mutation in KAL1 gene

HYPERPROLACTINEMIA

● Can be drug-induced or caused by tumors

● Pituitary tumors

● Primary Hypothyroidism

decreased LH & testosterone

110 ng/dL

Average testosterone decline after 30 yrs old is (?) per decade

Also experience muscle loss and lesser bone density

type 2 diabetes

Pituitary disease that makes

○ ↓ Testosterone (Free or total serum); ↓ LH

○ Stem from insulin resistance, low SHBG

levels, inflammation, and ↑ estradiol levels

Opioid use

○ Caused by μ-opioid receptor–mediated suppression of pulsatile GnRH production

○ Reduced male fertility

○ Decreased sperm motility

○ Lower sperm counts

○ Abnormal sperm morphology

parenteral

replacement therapy that is injectable testosterone in muscle every few days

transdermal

daily skin patches that provide steady hormone levels w/ possible skin mild irritation

Buccal

tablets applied to gum/cheeck for slow absorption

subcutaneous

implanted under skin, long lasting pellets

Cutaneous/Testosterone gel

require stable levels and caution due to transfer through skin contact