Unit V: Development Sex Hormones Chapter 26: pp. 966-967 Chapter 16: pp. 569.
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Transcript of Unit V: Development Sex Hormones Chapter 26: pp. 966-967 Chapter 16: pp. 569.
Essence of Sex
• Reproduction
– great variety of methods
asexual vs. sexual
• Sexual reproduction
– each offspring has 2 parents
– provides genetic diversity
Functions of Reproductive System
1. Produce and nurture sex cells
2. Transport gametes to site of fertilization
3. Secrete hormones
– Secondary sex characteristics
– Reproductive physiology
Two Sexes
• Gametes combine to form a zygote
1. Motility to achieve contact
• has Y chromosome
2. contains nutrients for developing embryo
• lacks Y chromosome
• in mammals female also provides shelter for developing embryo (uterus and placenta)
Role of Sex Chromosomes
• Somatic cells contain 23 pairs of chromosomes
– 22 pairs of autosomes
– 1 pair of sex chromosomes (XY males: XX females)
• 50% sperm carry Y; 50% X
• all eggs carry the X chromosome
• Sex of child determined by type of sperm that fertilizes mother’s egg
• Meiosis – series of two cell divisions that cut chromosome number in half
– diploid haploid fertilization diploid
Hormones and Sex Differentiation
• Gonads begin to develop at 6 weeks• Gonadal ridges
– mesonephric ducts vas deferens– paramesonephric ducts (müllerian ducts) oviduct
• SRY gene– in males, codes for a protein (TDF) that causes development of
testes • secrete testosterone • secrete müllerian-inhibiting factor degenerates
paramesonephric ducts• Female development occurs in absence of androgens
Fig. 27.3-2
Ovaries
Efferent ductules
Epididymis
Urinary bladder
Seminal vesicle
Mesonephros
Gonadal ridge
Kidney
Mesonephric duct
7 to 8 weeks 8 to 9 weeks
Cloaca
Male Female
Paramesonephric(müllerian) duct
5- to 6-week embryo;sexually indifferent stage
Testes
Paramesonephricduct (degenerating)
Mesonephric ductforming theductus deferens
Urogenital sinusforming the urethra
Paramesonephricduct forming theuterine tube
Mesonephric duct(degenerating)
Fused paramesonephricducts formingthe uterus
Urinary bladder(moved aside)
Urogenital sinusforming the urethraand lower vagina
Adrenal Gland
Adrenal Cortex:
–sex steroids
• Skeletal growth and sustain adult bone mass
• Development of pubic, axillary hair, apocrine glands
• Sustain sex drive
•androgen – male sex hormones
DHEA testosterone
Meets 50% requirement in women
•estrogen (estradiol)
Important after menopause
Adrenogenital Syndrome (AGS)
•Hypersecretion of androgens
•In children:
–Causes enlargement
–Premature onset of puberty
•In women and fetus:
–Masculinizing effects
Female Sex Hormones
• Estrogens – estradiol, estrone, and estriol
• Progesterone– changes in uterus during menstrual cycle (pregnancy)– affects mammary glands– regulates secretion of LH and FSH
• Androgens– development of female skeleton
• Inhibin
Responses to Estrogens in FemalesIntegumentary System
Produce vellus hairs, terminal hair in axillae and genital areaInitial development of the mammary glands
Skeletal System
Muscular System
Cardiovascular System
Respiratory System
More rapid epiphyseal closure Thus skeletal growth is brief
Growth of skeletal muscle fibersThus increasing strength and endurance
At puberty, activates CNS centers involved in female sexual drive and sexual behaviors
Reproductive System
Menstrual cycle ↑ risk of iron-deficiency anemiaEstrogens ↓ plasma cholesterol levels and slow the formation of plaque within arteries.
Less growth of the larynx and vocal cordsThus females have higher-pitched voices
Thicken of the myometrium↑ blood flow to the endometriumDevelopment of accessory reproductive structures
Nervous System
Female Sex Hormones
Release of Gonadotropin-Releasing Hormone (GnRH)Stimulates the production andsecretion of FSH and the production—but not the secretion—of LH.
HYPOTHALAMUS
GnRH
FSHProduction of LHSecretion of LH
Negative feedback
OVARY• Follicle development
• Inhibin• Estradiol
• Ovulation
• Corpus luteum
Progesterone
Beforeday 10
Afterday 10
KEYStimulationInhibition
Secondary Sexcharacteristics
ReproductiveSystem
Stimulation ofendometrial growth and secretion
ANTERIOR LOBE OFPITUITARY GLAND
The Gonads:Ovaries
Responses to Testosterone in MalesIntegumentary SystemTerminal hairs on the face and chest, axillae and genital areaAdipose tissues respond differently totestosterone than to estrogens
Skeletal System
Muscular System
Nervous System
Cardiovascular System
Accelerates bone deposition and skeletal growthPromotes closure of the epiphyseal cartilages
Stimulates the growth of skeletal muscle fibers
A t puberty, activates the CNS centers concerned with male sexual drive and sexual behaviors.
Stimulates erythropoiesis, thereby increasing bloodvolume and the hematocrit.
Respiratory System
Reproductive System
Stimulates disproportionate growth of the larynxThickening and lengthening of the vocal cordsGradual deepening of the voice
Development of the accessory reproductive glandsHelps promote spermatogenesis.
Male Sex Hormones
The Gonads:Testes
GnRHHYPOTHALAMUS
Negative feedback
Released relatively steady.
ANTERIOR LOBE OF THE PITUITARY
GLAND
LH
FSHTargets seminiferous tubules.
KEYStimulationInhibition
Negative feedback
Sustenacular Cells
Inhibin
Interstitial CellTestosteroneTESTES
Respond to factors released by developing spermatozoa
Androgen-binding protein (ABP)binds androgens ofseminiferous tubulesMaturation ofspermatids.
Spermatogenesis and spermiogenesis.
Peripheral Effects
Nervous System
Skeletal System
Secondary sex characteristics
Reproductivesystem
Androgen-Insensitivity Syndrome(Testicular Feminization)
•Genetically male
•Target cells lack receptors for testosterone
•Female anatomy
–no menstruation or uterus
–presence of testes in abdomen
Overview of Reproductive System
• Primary sex organs
– produce gametes
• Secondary sex organs
– male - ducts, glands, penis
– female - uterine tubes, uterus and vagina
• Secondary sex characteristics
– develop at puberty to attract a mate
• pubic, axillary and facial hair, scent glands, body morphology and low-pitched voice in males