Development And Differentiation Flashcards
What is SRY
Sex determining region Y
Region of Y chromosome that produces testis determining factor- promote development of testes
How many chromosomes
46 split 23/23
What gamete determines sex
Sperm
Define genetic, gonadal, phenotypic sex
Genetic sex- sex chromosomes
Gonadal sex- gonads- primary sex organs (testes or ovaries)
Phenotypic sex- internal/external genitalia
What is Turner’s Syndrome, name physical features
XO: Missing a sex chromosome (45) (1 in 2500 female births)
Physical features:
Primary amenorrhea (no menstrual cycle)
Infertility common
Typical external genitalia (small, immature)
Requires hormone therapy for breast development, menstruation and treatment of infertility
Inadequate estrogen production (weak bones, short stature, scoliosis)
Neck webbing (pterygium colli)
Increased risk of cardiac and renal defects (estrogen cardio protective)
What is Klinefelter syndrome, describe physical characteristics
XXY: extra X chromosome (47) (1 in 500 male births)
Most common sex abnormality fewer than 26% diagnosed
Physical characteristics:
No obvious facial dysmorphology
Tall stature
Small testes (usually infertile 95-99%)
Broad lips
Sparse body hair
Androgen, low serum T levels
Elevated gonadotropins
Azoospermia (low FSH and LH)- lack of sperm in semen
Gynecomastia (inc breast tissue) in late puberty
Psychiatric disorders more common
What is triple X Syndrome, describe physical characteristics
XXX (47): extra X (1 in 1000 female births/5-10 girls born in US daily)
Most undiagnosed- common abnormality
Physical characteristics:
May be taller
May result in kidney problems or seizures 10%
May cause developmental delays (speech, language, motor skills)
No unusual physical features
Psychological problems- anxiety, depression
Normal sexual development
Fertility normal (maybe ovarian problems)
What sex does early fetal development produce? What period is considered early development?
Undifferentiated development
Less than 9 weeks
What does gonadal development determine? How does it do this?
Determines phenotype
Based on endocrine and paracrine secretions produced by the gonad
What are germ cells
Undifferentiated reproductive cells
Explain male gonadal development
Germ cells migrate to cortex
Differentiate to spermatogonia
Sertoli cells produce AMH (anti-mullerian hormone)
Leydig cells produce testosterone (5alpha reductase converts to DHT for further genital development)
What do Sertoli cells produce
Anti mullerian hormone
What do Leydig cells produce
Testosterone
Explain female gonadal development
Medulla regresses and cortex thickens
Germ cells differentiate to primary oocytes
Components of male internal genitalia, what cells produce them
Wollfian development (Vas deferens)
Seminal vesicles
Ejaculatory ducts
- by Leydig cells
Female internal genitalia
Mullerian ducts- including Fallopian tubes, uterus, upper third vagina
What degenerates the Müllerian ducts
AMH
What is the other term for wollfian ducts
Vas deferens
What internal ducts is a fetus born with
Müllerian ducts and wollfian ducts
What features does an individuals who has an androgen receptor deficiency
Express XY
Male gonads (testes)
Wolffian degenerates
Mullerian degenerates
Female external genitalia
When do the testes descend
Final month of fetal development
What was Alfred Jost’s research
Castrate rabbits in utero
Discovered that the absence of SRY gene determined gender
Testosterone develop wolffian ducts but doesn’t degenerate mullerian
What causes wolffian development
Testosterone
What degenerates Müllerian ducts
AMH
What is required for male inner genitalia development
TDF (SRY)
What hormone determines external genitalia
DHT allows male
Female is default
Outcome of Male early castrate
No testes
Internal: No T/AMH- has Müllerian ducts (wolffian ducts can’t develop without T)
External: No DHT- default female
Outcome of Female early castrate
No ovaries
Internal: No T/AMH- Müllerian ducts
External: default female (no DHT)
Outcome of Male right unilateral early castrate
No left testes, has right
L internal: Yes T/AMH- wolffian duct
R internal: Müllerian duct (no T/DHT, female default)
External: Yes T/DHT- male
Outcome of male early castrate and testosterone
Androgens (T)- wolffian ducts
No AMH- Müllerian ducts
External: male/intersex
Outcome of female given testosterone
Androgens (T)- wolffian ducts
No AMH- Müllerian ducts
External: ambiguous/intersex
Outcome of Female left unilateral castrate
No left ovary, yes right ovary
Internal: No T/AMH- Müllerian ducts (wolffian degenerate)
External: female fully formed
What does 5 alpha-reductase deficiency cause
Lack of DHT (can’t convert T)
Intersex often raised female
What is the Cloaca
Tubular structure
Undifferentiated eventually becomes end of GI, external genitalia, pelvic region (urethra, prostatic urethra), phallic region (vagina, penile urethra)
What different m/f structure is made from the same undifferentiated tissue
Glans penis and clitorus
Name of castrated man- provide height change and when castrated
Alessandro Moreschi
Castrated after development but before puberty
Grew taller
Castrated provided higher pitch voice
Births of chromosomes/genitals not fitting definition f/m
1/300 births
What is the Prader Scale
Scale of virilization of the external genitalia- ambiguous genitalia
No virilization - female (fully developed)
Stage 5 - male
Sexual differentiation of brain (sexual dimorphic nuclei)
INAH3 - larger in males
Pre-optic area of hypothalamus
Development influenced by gonadal steroids
Sexual dimorphism in humans
Secondary sexual characteristics
Cognitive differences/ neurological differences
Behavioural differences
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