Función Endocrina Gonadal y Reproducción Sexual, UIB

Fisiología Humana y Reproducción Sexual

Fisiología humana (22705)
UIB
Universitat
de les Illes Balears

Conceptos Clave de la Reproducción Sexual

• Reproducción sexual
• Células germinales: Células gonadales indiferenciadas destinadas a producir óvulos y
  espermatozoide.
• Gónadas: Órganos que producen los gametos.
  Gametos: Células encargadas de la reproducción (óvulos y espermatozoides).
• Genitales internos: Glandulas y conductos accesorios que conectan las gonadas con el
  medio externo.
• Genitales externos: Conjunto de estructuras reproductivas externas
  Teoría del gen egoísta y/o variabilidad de la población

Determinación del Sexo Cromosómico

Female parent
Male parent
XX
XY
X
Eggs
X
X
Sperm
Y
XX Female offspring
11
12
13
14
15
16
17
18
X
19
20
21
22
Copyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
3
7
9
10
6
8
Y
XY
Male offspring

Determinantes de la Diferenciación Sexual

Determinación sexual del zigoto > Sexo cromosómico
Desarrollo gonadal -> Sexo gonadal
Desarrollo de los conductos internos sexuales -> Sexo hormonal
Estructura de los genitales externos > Sexo genital
Feminización o masculinización puberal -> Sexo hormonal
Fertilidad -> Sexo reproductivo
Otros -> Sexo comportamental, sexo social, identidad sexual, ...

Clasificación de los Caracteres Sexuales

Clasificación clásica:
· Primarios
· Secundarios
Categorías de los caracteres sexuales:
· Primarios o genéticos
· Secundarios
· Terciarios o genitales
· Cuaternarios o aparentes
· De quinto orden o psíquicos

Proceso de Determinación Sexual

X
Y
Espermatozoide
Óvulo
Óvulo Espermatozoide
Cuerpo de Barr
XY
XX
Cigoto
Cigoto
X
TDF
Gónadas
indiferentes
No TDF
Testículos
Ovarios
(Los folículos no se desarrollan
hasta el tercer trimestre X)
Túbulos
seminíferos
Células
intersticiales
(a)
(b)
Se desarrolla en el embrión
en etapa inicial

Desarrollo de Órganos Internos

(a) Development of internal organs
Bipotential stage: 6 weeks of fetal development
The internal reproductive organs have the potential
to develop into male or female structures.
Müllerian duct
FEMALE
Wolffian
duct
MALE
Bipotential
gonad
Kidney
1
Gonadal cortex becomes
ovary in the absence
of SRY protein.
000
SRY protein in a male
embryo directs the
medulla of the
bipotential gonad
to develop into testis.
Cloacal
opening
2
Absence of testosterone
causes Wolffian duct
to degenerate.
Müllerian duct
Wolffian
duct
2
Anti-Müllerian hormone
from testis causes the
Müllerian ducts to
degenerate.
Uterus
10 WEEKS
Ovary
Prostate
3
Seminal vesicle
Fallopian tube
(from Müllerian
duct)
Vas deferens
Uterus
Testis
Vagina
AT BIRTH
Epididymis
3
Absence of anti-Müllerian
hormone allows the
Müllerian duct
to become
the fallopian
tube, uterus,
and upper part
of the vagina.
0
Testosterone from
testis converts Wolffian
duct into seminal
vesicle, vas deferens,
and epididymis. DHT
controls prostate
development.
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
SRY gene
1
Testis

Mecanismos de Diferenciación Sexual

KEY
Sex-determining
region of Y chromosome
in embryonic germ
cells (SRY gene)
Integrating center
Efferent pathway
Tissue response
produces
Testis-determining
SRY protein
initiates production of
Multiple proteins that
cause gonad medulla to
differentiate into a testis
SOX9, WT1, SF1
which has
Leydig
cells
Sertoli
cells
secrete
secrete
Testosterone
Anti-Müllerian
hormone
controls
causes
Development of
Wolffian duct into
accessory structures
Development of male
external genitalia
(via DHT)
Regression of
Müllerian duct
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.

Desarrollo de Genitales Externos

(b) Development of external genitalia
Genital tubercle
Urethral
groove
MALE
FEMALE
Labioscrotal
swelling
Anus
Urethral
fold
Clitoris
Penis
Urethral fold
Bipotential stage
(6 week fetus)
Urethral
fold
Labioscrotal
swelling
Labioscrotal
swelling
Anus
Anus
10 WEEKS
DHT causes
development
of male external
genitalia.
1
In the absence
of androgens,
the external genitalia
are feminized.
Clitoris
Glans penis
Labia
majora
Urethral
opening
Shaft of penis
Labia
minora
Vaginal
opening
*
Anus
Anus
2
AT BIRTH
The testes descend
from the abdominal
cavity into the
scrotum.
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
1
Scrotum

Diferenciación Sexual: Estructuras Bipotenciales

TABLE 26-1
Sexual Differentiation
MALE
BIPOTENTIAL STRUCTURE
FEMALE
Glans penis
«- Genital tubercle
Clitoris
Shaft of penis
< Urethral folds and groove ->
Labia minora, opening of vagina and urethra
Shaft of penis and scrotum
« Labioscrotal swellings ->
Labia majora
Regresses
« Gonad (cortex) ->
Forms ovary
Forms testis
«- Gonad (medulla) ->
Regresses
Becomes epididymis, vas deferens,
and seminal vesicle (testosterone
present)
« Wolffian duct ->
Regresses (testosterone absent)
Regresses (anti-Müllerian hormone
present)
<- Müllerian duct ->
Becomes Fallopian tube, uterus, cervix,
and upper 1/3 of vagina (anti-Müllerian
hormone absent)
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.

Cronograma del Desarrollo del Sistema Reproductor

Cuadro 20-1 | Cronograma del desarrollo del sistema reproductor
Tiempo aproximado después de la fecundación
Cambios del desarrollo
Días
Trimestre
Indiferente
Hombres
Mujeres
19
Primero
Las células germinales emigran desde
el saco vitelino
25-30
Los conductos de Wolff comienzan a
desarrollarse
44-48
Los conductos mullerianos comienzan
a desarrollarse
50-52
Se desarrolla el seno urogenital y el
tubérculo
53-60
Aparecen los túbulos y las células de
Sertoli
Comienzan su regresión los conductos
müllerianos
60-75
Aparecen las células de Leydig y
comienza la producción de
testosterona
Comienza la formación de la vagina
Crecen los conductos wolffianos|
Comienza la regresión de los
conductos wolffianos
105
Segundo
Comienza el desarrollo de los
folículos ováricos
120
Se forma el útero
160-260
Tercero
Los testiculos descienden hacia el
escroto
Concluye la formación de la vagina
Ocurre el crecimiento de los genitales
externos
Fuente: Reproducido con autorización, de Annual Review of Physiology, Volume 40, p. 279. Copyright @ 1978 por Annual Reviews, Inc.

Meiosis y Gametogénesis

MALE
STAGE OF CELL DIVISION
FEMALE
Spermatogonium
MITOSIS
Germ cell proliferation
Embryo
46 chromosomes
per cell (only two
shown here)
Y
Y
X
Spermatogonia
Oogonia
Primary
spermatocyte
YK
Sister
chromatids
Sister
chromatids
XK
Primary
oocyte
1
Reproductive adult
First meiotic
division
X
Secondary
spermatocyte
X
Primary gamete divides
into two secondary gametes.
X
Secondary
oocyte
(egg)
First
polar
body
23 chromosomes
duplicated
· (may not
`,
occur)
-
Y
Second meiotic
division
Disintegrates
Spermatids
develop into
Secondary gamete divides.
X
Egg released
from ovary at
ovulation
Sperm
23 chromosomes
(haploid)
/
One primary spermatocyte
yields 4 sperm.
One primary oocyte
yields 1 egg.
-
Second polar body
disintegrates.
Unfertilized egg passes
out of body.
Zygote
X
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
Reproductive adult
X
MEIOSIS
DNA replicates but
no cell division occurs.
2 sets of 46
chromosomes
Embryo
46
(diploid)
Oögonium
FERTILIZATION

Órganos Reproductores al Nacimiento

Urinary bladder
Uterine
tube
Seminal vesicle
Prostate gland
Uterus
Bulbourethral
gland
Urinary bladder
(moved aside)
Ductus deferens
Urethra
Vagina
Efferent ductules
Urethra
Epididymis
Testis
Hymen
Penis
Vestibule
At birth
male development
Ovary
At birth
female development

Programación y Desarrollo Sexual

Early life programming
Juvenile hiatus
Adult activation
Critical
window
-
Male
-
- Female
Conception
Birth
Developmental age
Puberty
Sex differences in:
Sex differences in social play
· Apoptosis
· Neurogenesis and gliogenesis
· Dendritic growth
· Myelination
· Synaptogenesis
· Synaptic pruning
Nature Reviews | Neuroscience
Testosterone (T) =
Brain Sensitivity to T-
Perinatal
Prepuberta
Pubertal/
Adolescent
Adult
0 1 2 3 4 5 6 7 8 9 10
Age (weeks)
· Activation of sex-specific
circuits for mating
· Modulation of social and
emotional behaviours
· Changes in cognitive
learning strategies
Gonadal hormone levels

Cambios en el Desarrollo Sexual por Edad

Age (years)
9
10
11
12
13
14
15
16
17
Height spurt
Girls
9.5-14.5
Menarche
10-16.5
Breast stages
2
3
4
5
8-13
13-18
Axillary hair
2
3
4
5
Pubic hair stages
Height spurt
10.5-16
13.5-17.5
Boys
Penis
10.5-14.5
12.5-16.5
Testis
9.5-13.5
13.5-17
Axillary and facial hair
2
3
4
5
Pubic hair stages
9
10
11
12
13
14
15
16
17
Age (years)

Regulación Hormonal del Desarrollo Sexual

Inhibition
From the
gonad:
Insignificant
Insignificant
Dominant
From CNS:
Dominant
Decreasing
Insignificant
-
Hypothalamus
Hypothalamus
Hypothalamus
GnRH
+
GnRH
+
GnRH
+
-
Activating +
Inhibitory -
+
Activating +
Inhibitory
+
Activating +
Inhibitory-
+
Pituitary
Pituitary
Pituitary
+
LH
FSH
+
LH
FSH
B
Gonads
Gonads
Pre-puberty
-
-
-
+
ILH
1 FSH
Gonads
Puberty
Adulthood

Síntesis de Esteroides Sexuales

Cholesterol
Progesterone
*
Testosterone
Dihydro-
testosterone
(DHT)
aromatase
Corticosterone
Cortisol
Estradiol
KEY
*
5x-reductase
Aldosterone
Intermediate steps
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.

Regulación de la Liberación de Gonadotropinas

CNS
Internal and
environmental
stimuli
GnRH
Hypothalamus
Short-loop negative feedback
KEY
0
Stimulus
Anterior
pituitary
Integrating center
Efferent pathway
Effector
Long-loop feedback
may be negative
or positive
LH
FSH
Tissue response
- -
Gonads
(ovaries or testes)
-
-
Endocrine
cells
------
Gamete
production
Steroid and
peptide hormones
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.
Females only

Efectos de los Esteroides Sexuales en Gonadotropinas

TABLE 26-2
Effects of Sex Steroids
on Gonadotropin Release
STEROID
HORMONE
EFFECT
GONADOTROPIN
LEVEL
Low estrogen
or androgen
Absence of negative
Increases
feedback
Moderate
estrogen
or androgen
Negative feedback
Decreases
High androgen
Negative feedback
Decreases
Sustained high
estrogen
Positive feedback
Increases
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.

Anatomía del Sistema Reproductor Masculino

(a)
Urinary bladder
Ureter
Pubic symphysis
Seminal vesicle
Vas deferens
Ejaculatory duct
Urethra
Rectum
Penis
Prostate gland
Bulbourethral
gland
Epididymis
Testis
Scrotum
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.

Composición del Semen

TABLE 26-3
Composition of Semen
COMPONENT
FUNCTION
SOURCE
Sperm
Gametes
Seminiferous
tubules
Mucus
Lubricant
Bulbourethral
glands
Water
Provides liquid
medium
All accessory
glands
Buffers
Neutralize acidic
environment of
the vagina
Prostate,
bulbourethral
glands
Nutrients
Nourish sperm
Fructose
Citric acid
Seminal vesicles
Prostate
Vitamin C
Carnitine
Seminal vesicles
Epididymis
Enzymes
Clot semen in
vagina, then
liquefy the clot
Seminal vesicles
and prostate
Zinc
Unknown; possible
association with
fertility
Unknown
Prostaglandins
Smooth muscle
contraction; may
aid sperm transport
Seminal vesicles
Copyright @ 2007 Pearson Education, Inc., publishing as Benjamin Cummings.