Reproduction during the Lifetime

What do the nervous and endocrine systems do?

work together to coordinate and regulate body functions

How does the nervous system communicate?

rapidly through nerve impulses and neurotransmitter release at synapses

How does the endocrine system communicate?

slowly through hormones released in bloodstream

What body processes are regulated by hormones?

internal environment, energy balance, muscle activity, gland secretion, immunity, growth, reproduction, circadian rhythms

What is required for a hormone to affect a cell?

have the appropriate hormone receptor

What are the three types of hormone signalling shown?

endocrine, autocrine, paracrine

How do water-soluble hormones act?

bind to receptors and activate a cascade of intracellular events involving second messengers

How do lipid-soluble hormones act?

enter cells and bind intracellular receptors, affecting gene expression and protein production

What is the general role of feedback in endocrine regulation?

regulates hormone secretion, maintains homeostasis

What are the two main functions of the gonads?

produce gametes and reproductive hormones

What are the male and female gonads?

testes in males, ovaries in females

What are the main endocrine structures controlling reproduction?

hypothalamus, pituitary gland, gonads

What hormone is released by the hypothalamus to regulate gonadotrophin secretion?

gonadotrophin releasing hormone

Which cells of the anterior pituitary produce gonadotrophins?

gonadotrophs

What are the two gonadotrophins?

fsh, lh

What do FSH and LH act on?

the gonads

What is the basic reproductive endocrine pathway?

hypothalamus, gnrh, anterior pituitary, fsh/lh, gonads

What are the three groups of sex steroids covered?

androgens, oestrogens, progestagens

Where are androgens produced?

mainly in testes

What is the main androgen produced by the testes?

testosterone

What can testosterone be converted into?

5a-dihydrotestosterone

What reproductive functions are associated with testosterone?

male sex development, secondary sex characteristics, spermatogenesis

What other effects of testosterone were listed?

libido, muscle development

What is the main role of oestrogens?

develop and maintain female characteristics, fertility

What are the three oestrogens listed?

oestradiol, oestrone, oestriol

Where is oestradiol mainly produced?

granulosa cells

What are the reproductive roles of oestrogen?

female sex development, secondary sex characteristics, menstrual cycle regulation, endometrial growth

What other function of oestrogen was listed?

bone health

Where is progesterone mainly produced?

corpus luteum, placenta

What is progesterone associated with?

preparation and maintenance of pregnancy

What is sex determination?

bipotential gonad becomes testis or ovary

What is sex differentiation?

development of genital structures

How is normal sex determination genetically controlled?

by sex hormones

What are the usual sex chromosome combinations?

xx female, xy male

What is SRY?

sex determining region on y chromosome

What is the role of SRY?

development of testes

What two duct systems are present early in development?

mullerian and wolffian ducts

Which duct is associated with female internal genitalia?

mullerian duct

Which duct is associated with male internal genitalia?

wolffian duct

Which testicular cells produce anti-Müllerian hormone?

sertoli cells

What does anti-Müllerian hormone cause?

regression of mullerian ducts

Which testicular cells produce testosterone?

leydig cells

What does testosterone do to the Wolffian ducts?

maintain and promotes development

What do the Wolffian ducts develop into?

epididymis, van deferens, seminal vesicles

What happens to the Wolffian ducts during female differentiation?

regress from about 10 weeks

What do the Müllerian ducts develop into?

fallopian tubes, uterus, cervix, upper vagina

When are both Müllerian and Wolffian ducts present?

during early undifferentiated stage, 5-6 weeks

What is the developmental origin of male and female external genitalia?

from single bipotential cursor

What structures are present in the bipotential external genitalia?

genital tubercle, urethral folds, urethral groove, labioscrotal swellings

What do the urethral folds become in females?

labia minora

What do the labioscrotal swellings become in females?

labia majora

What does the genital tubercle become in females?

clitoris

What happens to the urethral folds in males?

fuse to form the shaft of penis

What happens to the labioscrotal swellings in males?

fuse to form the scrotum

What does the genital tubercle become in males?

glans penis

What drives male external genital differentiation?

androgen

What is androgen insensitivity syndrome?

xy has testes, cannot respond normally to androgens because of an androgen receptor mutation

What happens to external genital development in androgen insensitivity syndrome?

external genitalia appear female

What is puberty?

physical, emotional and sexual transition from childhood to adulthood

What happens to the reproductive system during childhood?

inactive, goes to sleep

What happens to the reproductive system at puberty?

reawakened, leading to sexual maturation

What happens to gonadotrophin levels during childhood?

remain very low

What is the first endocrine sign of puberty?

increase in plasma lh

What causes the increase in LH at puberty?

increase in gnrh release

When does gonadotrophin secretion initially occur during puberty?

at night during sleep

What happens to LH secretion in late puberty?

daytime lh pulses increase

What happens to sex steroid levels during puberty?

increase in response to increased lh

What are secondary sexual characteristics?

physical characteristics developed during sexual maturation

What is Tanner staging used for?

assess sexual development, detect abnormalities, compare development

What is the sequence of female pubertal events shown in the lecture?

breast development, pubic hair, growth spurt, menarche

What is the first physical sign of female secondary sexual maturation?

breast development at 10-11 years

What causes breast development?

oestrogen secretion

What contributes to full breast development?

ovulation followed by progesterone secretion

When does pubic hair usually appear?

within 6 months of breast development

What causes pubic hair development?

exposure of hair follicles to androgens

When does axillary hair generally follow pubic hair?

one year later

When does the female growth spurt typically occur?

around 11-12 years

What hormones stimulate the growth spurt?

steroid hormones

What causes epiphyseal closure?

oestrogen

What is menarche?

first menstrual bleeding

What is the average age of menarche?

12-13 years

When does first ovulation usually occur relative to menarche?

6-9 months after

When are regular ovulatory cycles usually established?

1-2 years after menarche

What is the first sign of male secondary sexual development?

testicular enlargement

What causes increased testicular size during puberty?

increased gonadotrophin secretion

When does penile enlargement begin?

within one year of testicular enlargement

What causes penile enlargement?

testosterone

When does pubic hair appear after testicular enlargement?

6 months after

What other physical changes occur during male puberty?

axillary and facial hair develop, larynx becomes thicker and larger

What is spermarche?

first spontaneous ejaculation of sperm filled fluid

At approximately what age is motile sperm seen in urine?

13-14 years

What trend has occurred in the age of menarche?

earlier menarche

What is thought to contribute to earlier menarche?

improved nutrition, healthcare, social living conditions

Why is a critical weight important for female puberty?

sufficient energy storage required to sustain pregnancy

What is the approximate mean weight at the beginning of menarche?

47kg

What is precocious puberty?

physical and hormonal signs of puberty before 7 years in females or 9 years in males

What is usually involved in precocious puberty?

gnrh dependent problem

What can cause extreme cases of precocious puberty?

hypothalamic tumor

What is delayed puberty?

lack of hormonal and physical signs of puberty at 13 years in females or 14 years in males

What causes delayed puberty in the lecture?

low gonadotrophin signals for sex steroid secretion