Lecture 19 Flashcards
What is the definition of sex at an anatomical level?
Gonadal: internal genitalia (ovaries/testes)
Morphological: external genitalia
What is sex at the chromosomal level?
Defined based on the presence of XX or XY chromosomes in somatic cells
What is the difference between X and Y chromosomes? What are the similar structures?
Size and genetic material; 2 pseudoautosomal regions
How does SRY gene expression influences hormone production/ sex determination?
It initiates male sex development; if the SRY gene is +, leads to testes determining factor (TDF,SOX9+), if SRY-, no TDF (SOX9-)
How is testosterone produced in a fetus?
Testosterone is produced by leydig cells
How is estrogen produced in a fetus?
Estrogens are produced by follicular cells
What is chromosomal aneuploidy?
An abnormal number of chromosomes in a cell
What is dosage compensation?
Ensures that XY males and XX females express the same amount of X chromosome— one of the two X chromosomes is inactivated (XCI)
What is a Barr body?
Dense heterochromatic structure formed by XCI in XX females
How do the levels of SHOX gene in the pseudo-autosomal region compare with each other?
They have comparable levels of SHOX gene
Where does sex development begin? What morphological/gonadal sex does it begin expressing?
The bipotential urogenital ridge at 6 weeks of gestational age; both male and female at the same time
What are Mullerian and Wolffian ducts?
Ducts located in the urogenital ridge that differentiate into female or male structures at week 7
What develops from a SOX9- gene?
Ovaries— germ cells develop oocytes, granulosa cells do not produce AMH and Müllerian ducts develop and wolffian ducts degrade
Testes— germ cells develop sperm; Sertoli cells produce AMH and wolffian ducts develop
What does the development of external genitalia depend on?
Androgens and estrogens
What produced androgens?
Leydig cells
What produces estrogen?
Follicular cells
What time are male and female external genitalia first visible by ultrasound?
11 weeks
How many types of estrogens exist? What are they?
E1. Estrone
E2. Estradiol
E3. Estriol
What turns testosterone into estrogen?
Aromatase
What is the function of testosterone? What is the function of estrogen?
Testosterone: promotes protein synthesis, increases bone density and muscle mass, male sex organ development
Estrogen: important for bone health
How are steroids synthesized?
Modifications of cholesterol
What are the five stages of post-natal development?
- Neonatal: birth to 1 month
- Infancy: 1 month to 1 year
- Childhood: 1 year to onset of puberty
- Adolescence: puberty to when growth is completed
- Maturity: when growth is completed
What is the difference between organizational and activation all hormonal effects?
Organizational: during the critical window, while neural structures are being established
Activational: puberty occurs in puberty with a rise in hormones
How do sex hormones affect body systems in puberty?
- Hypothalamus increases GnRH— FSH and LH
- Gamete production initiated
- Sex hormones are released and secondary sex characteristics and behaviour
- Accelerated growth rate
