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101 Cards in this Set

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The four major functional components of the male repoductive system
1. Testes (male gonads)
2. A paired system of ducts
3. Two exocrine glands
(Paired seminal vesicle
and the single prostate)
4. The penis
Functions of the four components
The testes or male gonads: produce spermatozoa and secrete testosterone

A paired system of ducts: collect, store and conduct spermatozoa from each testis

Exocrine glands: secrete a nutritive and lubricating fluid medium in which spermatozoa are conveyed to the female reproductive tract

The penis: organ of copulation
Temperature differance in scrotum?

why?
2 degrees C below abdominal temp.

Necessary for normal spermatogenesis
Development of the testes
Decends along a tortuous path from posterior wall of the peritoneal cavity to the scrotum.

Almost completely surrounded by a serous cavity which is an extension of the peritoneal cavity= tunica vaginalis
Three layer of membranes that comprise the testicular capsule
Tunica vasculosa

Tunica vaginalis

Tunica albuginea
Tunica Albuginea
Dense, fibrous connective tissue layer that encapsulated the testis= forms lobules
Testes two functional units
1.Spermatogenic or seminiferous tubules: a network of tubules that produce and transport the sperm to the excretory-ejaculatory ducts.

2. Leydig cells: interstitial cells that contain the enzymatic machinery for the production of androgenic hormones.
Seminferous Tubules
cell types and function
1. Germ Cells: site of spermatogenesis
2. Sertoli cells: provide structural and metabolic support for the developing spermatogenic cells
Spermatogenesis occurs in an orderly fashion.
List steps
1.Formation of spermatogonia
2.primary spermatocytes (46 chromosomes)
3.Secondary spermatocyes(23 chromosomes)
4.Spermatids (23)
5.Spermatozoa (23)
Spermatogonia
Location
next to the basal lamina of the seminiferous tubules
Sertoli Cell functions
1. Formation of the blood testis barrier
2. Production of androgen binding hormone
3. Production of Inhibin
4.Production of seminiferous tubule fluid
5.Supporting role for germ cells
6.Aromatization of androgens to estrogen
7.Production of antimullerian hormone
blood-testis barrier
what cells?

What function?

Type of junction?
Sertoli cells.

Prevents proteins and other large molecules from passing from the interstitial tissue.

Tight Junctions
Basal compartment contains?
Spermatogonium
Adluminal compartment contains?
Spermatocyte
Spermatid
Spermatozoa
Androgen Binding protein serves to
maintain high testosterone levels within the testis and seminal fluids
Inhibin mechanism?
Serine/Threonin kinase receptor
Which inhibin is the physiologically inmportant one in males?
Inhibin alpha Beta B
Inhibin is produced by _______ cells in respose to ____ stimulation
Sertoli

FSH
Seminiferous tubule fluid contains __________ and inhibits __________ and _________, thereby prolonging viability.
Nutrients

Capacitation

Motility
Sertoli cells provide support for germs cells through
extension of cytoplasm
Leydig cells are under control of what pituitary hormone?
LH
Pampiniform plexus
Testicular veins
Countercurrent exchange of heat and testosterone in testis leads to 2 gradients...??
1. Temperature
2.Androgen
Testes two main functions?
Exocrine: spermatogenesis
Endocrine: Steroidogenesis
Spermiogenesis
Germ cell dfferentiation from secondary spermatocytes to spermatozoa
As spermatid matures into a sperm, what differences are seen?
Size of nucleus decreases

Prominent Tail is formed

Chromtin material in nucleus condenses

Nucleus occupies an eccentric position
The Acrosome of the sperm contains?
It acts as a lysosome and contains two proteolytic enzymes:

1.Acrosin
2.Hyaluronic
Spermiation
Mature Spermatozoa are released from the Sertoli cells and become free in the lumens of the tubules.
Crytorchidism
When testes remain in the adbomen, degeneration of the tubular walls and sterility occurs.
Spermatogenesis depended on three types of hormones?
FSH, LH and androgens
FSH acts directly on the
spermatogenic tubules
FSH binds to _____ cells
Sertoli
FSH on Sertoli cells uses what mechanism
Adenylate cyclase, incr of cAMP, activation of protein kinases and phosohorylation.
FSH stimulates
mitosis of Sertoil cells
(incr # during puberty)
FSH promotes
maturation of Sertoli cells and the development of tight junctions b/w them
FSH initiates
spermatogenesis

(and sperm maturation)
FSH also promotes
production of ABP by Sertoli cells
FSH stimulates sertoli cells in seminiferous tubules to produce a hormone?
Inhibin
LH influences spermatogenesis INDIRECTLY by stimulating production of what hormone in the Leydig cells?
Testosterone
Without testosterone, spermatogenesis is arrested at eaht stage?
Primary spermatocyte
Sperm storage sites
Epididymis
Ampulla
Normal sperm count?
60 million per ml
No flashcards on Accessory structures-read!
No flashcards on Accessory structures
Leydig cells have LH receptors but not
FSH receptors
LH stimulates steroidogenesis by what mechanism
cAMP mediated
Rate limiting step in testosterone biosynthesis?
Side chain clevage of cholesterol to pregnenolone.

(by Desmolase)
Testes produce ___% of testosterone...the rest in the adrenals
95%
Sertoli and Leydig cells produce 10-15% of serum estrogens in normal adult men.rest in....
Adipose (fat) tissue
Two other androgens (besides Testosoterone) produced in testis.
1. DHEA
2.Androstendione
Testosterone as a neg. feedback on.
1.
2.
1. Hypothalmus to slow GnRH
2.Pituitary to slow LH

(if GnRH and LH low= less testosterone)
the major route of steroid exit from the testis to general circulation is via
the spermatic venous blood
Testosterone acts as a negative feedback on LH and GnRH....what also exerts a negative feedback on LH?
DHT
Inhibin inhibits?
FSH
Activin
antagonizes inhibin B = FSH release.
How many carbons does testosterone have
19
What pathway does testosterone follow?
Delta 5
LH regulates the rate of the rnx of the conversion of cholesterol to pregnenolone and thus
controls the overall rate of testosterone synthesis
Oscillations of testosterone are essential for the function of the __________-________-__________ axis
hypothalmis-pituitary-gonadal
If GnRH pulses are less than 12 or more than 24 oscillations per 24 hours, the pituitary gland becomes
unresposive to GnRH and ceases to secrete enought LH to stimulate the testis
annual secretion pattern of androgens in males. highest in ___________, lowest in ___________
September-October

March-April
90% of the circulating androgens are bound to plasma proteins _______________ & _______________
SHBG (sex hormone binding globuline) and albumin
Androgens affesct the liver production of SHBG by __________ production of SHBG.
Reducing

ie males with higher androgen levels ahve lower levels of SHBG and thus higher free androgens.
DHTis preferred in which tissues?
Prostate, hair, external genitalia.
Intratesticular androgen levels are more than ______ times greater than blood levels.
200
When testosterone acts on the Sertoli cells it stimulates the production of ___
ABP androgen binding protein)
The major PLASMA androgen binding protein is
SHBG!
_______ levels of testosterone are essential for epididymal function
high
__________ (which type testis vs circulating) levels of testosterone support function of the vas deferens.
Circulating
Prostate uses
A.testosterone
b.DHT
B. DHT

DHT causes growth and secretion of the prostate gland.
If the enzyme 5 Alpha-Reductase is reduced of absent, what happens to the prostate gland?
it never developes.

Also if 5@reductase is absent:
males have very scant facial,pubic & axillary hair.
What enzyme converts testosterone to DHT?
5 Alpha-Reductase
DHT does what in
1. the prostate
2. the scrotum
3. the penis
1. Prostate- causes growth and secretion

2.The scrotum- responsible for the thinning and development of folds to keep testes cool AND pigmentation of the scrotum.

3. Penis- Essential for enlargement of the penis at puberty.
Testosterone-->
1. W/ 5 Alpha reductase
2. W/ aromatase
1. DHT
2.Estradiol
DHT, in DHT sensitve cells seems to have a greater binding affinity (appx 10 fold) thus
DGT has more potency than testosterone in those tissues.
Androgens affect the liver production of SHBG by
reducing production of SHBG.
C21 steroids
Pregnenes
(Progestins, Corticoids)
C19 steroids
Androgens
C18 steroids
Estrogens
(Aromatized A ring0
Parent steroid
Cholesterol
Cholesterol is synthesized from
Acetic acid
Hydroxylase Func.
Adds a hydroxyl.

Essential step before removal of any carbon atoms.

Not reversible
Side chain cleavage enzyme

Function.

Name two
Remove peptide chains from the steroid nucleus.
(usually b/w two Carbons that hve been hydroxylated.

Not reversible.

1.Desmolase
2.Lyase
Oxido-reductase func.
(hydroxy-steroid dehydrogenase)
REVERSIBLE

1.Converts hydroxyl groups to keto groups
OR
2.Keto groups to hydroxyl
If oxido-reductase has NADP or NAD what happens?

If NADPH or NADH?
1. they are hydrogen donors so will form hydroxyl groups

2.Forms keto groups

MATTERS ON COFACTOR
Isomerase func.

What usually?
Shifts the position of the double bond

usually from 5-6 to 4-5

Not reversible
Aromatase func
Adds double bonds to make the A ring aromatic or cyclized.

Not reversible
Reductase
Breaks a double bond and adds a hydrogen.

Not reversible

Can incr or reduce activity of a steroid.
Cholesterol to pregnenolone
How important?

What enzymes? What order?

What # carbons after
1st step before any pathway!!

1.Hydroxylase- at c20 &c22
2.Side Chain cleavage enzyme- at C21

Leaves a 21 Carbon base (pregenes)

NOTE- Rate limiting step!
Pregnenolone to Progesterone

What enzymes? What order?
The two enzymes act as a complex.

1.Isomerase- shifts 5-6 to 4-5
2.Oxido-Reductase-
(cofactor NAD or NADP)
Leaves a keto group at C3
Pregnenolone to 17hydroxy pregnenolone

What enzymes? What order?
1.Hydroxylase - at C17

Predominant form!
Pregnenolone to Aldosterone

What enzymes? What order?
Goes from Pregenologe ---> Progesterone

Then
1.Hydroxylase-Hydroxylated at C21 =deoxycorticosterone
2.Hydroxylase-Hydroxylated at C11= corticosterone
3. Hydroxylase-Hydroxylated @ C18
4. Oxido-Reductase- hydroxyl to keto
Cortisol synthesis

What enzymes? What order?
FIRST- Progesterone to 17-hydroxy progeseterone( hydroyxylase)

1.Hydroxylase- C21
2.Hydroxylase- C11
=Cortisol
Cortisol synthesis

Once the molecule is initially hydroxylated atthe ___ position, this inbits the ___ so that aldosterone CANNOT BE PRODUCED!
C17

C18
The zona fasciculata of the adrenal cortex is rich in ___________ so therefore does not produce aldosterone.

Zona glomerulus proceeds to aldosterone
17 hydroxylases
Androgen Synthesis

Testosterone

What enzymes? What order?
Pregnenolone--->
17 hydroxy Pregnenolone

1.Side chain cleaving enzyme b/w C17 and C20 =DHEA
2.Isomerase &
3. Oxido-reductase = Androstenedione

4.Oxido-reductase at C17 to hydroxyl wit NADPH or NADH cofactors=
Testosterone!
Testosterone to DHT

What enzymes? What order?
Reductase at C4-5
Androstenedione is the primary androgen in
A.Males
B.Females
b.Females
Pregenolone--> progesterone-->
17hydroxyprogesterone--> Androstenedione---->Estrogen

Androstendione to estrogen

What enzymes? What order?
1.Hydroxylase- C19
2.Side-chain cleavage enzyme- C19 (=Nortestosterone)
3.Aromatase- A ring
=ESTROGEN

(with oxido-reductase C3 to estradiol)
The cyclized ring of aldosterone is the active form...what carbons cycle?
C11 & C18
Zona Fasciulata makes
cortisol

b/c high in 17 hyrdoxylases
Zona Glomerulosa makes
Aldosterone

low in 17 Hyrdoxylaes