1. Unit V: Development Sex Hormones
Chapter 26: pp
Chapter 16: pp. 569

2. Essence of Sex Reproduction great variety of methods
asexual vs. sexual
Sexual reproduction
each offspring has 2 parents
provides genetic diversity

3. Functions of Reproductive System
Produce and nurture sex cells
Transport gametes to site of fertilization
Secrete hormones
Secondary sex characteristics
Reproductive physiology

4. Two Sexes Gametes combine to form a zygote Motility to achieve contact
has Y chromosome
contains nutrients for developing embryo
lacks Y chromosome
in mammals female also provides shelter for developing embryo (uterus and placenta)

5. 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

6. 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

7. sexually indifferent stage
Fig
Mesonephros
Mesonephric duct
Gonadal ridge
Paramesonephric
(müllerian) duct
Kidney
Cloaca
5- to 6-week embryo;
sexually indifferent stage
Male
Female
Testes
Ovaries
Efferent ductules
Paramesonephric
duct forming the
uterine tube
Epididymis
Paramesonephric
duct (degenerating)
Mesonephric duct
(degenerating)
Mesonephric duct
forming the
ductus deferens
Fused paramesonephric
ducts forming
the uterus
Urinary bladder
Urinary bladder
(moved aside)
Seminal vesicle
Urogenital sinus
forming the urethra
Urogenital sinus
forming the urethra
and lower vagina
7 to 8 weeks
8 to 9 weeks

8. 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

9. Adrenogenital Syndrome (AGS)
Hypersecretion of androgens
In children:
Causes enlargement
Premature onset of puberty
In women and fetus:
Masculinizing effects

10. 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

11. Female Sex Hormones Responses to Estrogens in Females
Integumentary System
Produce vellus hairs, terminal hair in axillae and genital area
Initial 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 fibers Thus 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 anemia
Estrogens ↓ plasma cholesterol levels and slow the formation of plaque within arteries.
Less growth of the larynx and vocal cords
Thus females have higher-pitched voices
Thicken of the myometrium ↑ blood flow to the endometrium Development of accessory reproductive structures
Nervous System

12. ANTERIOR LOBE OF PITUITARY GLAND
Release of Gonadotropin- Releasing Hormone (GnRH)
Stimulates the production and secretion of FSH and the production— but not the secretion—of LH.
HYPOTHALAMUS
GnRH
FSH
Production of LH
Secretion of LH
Negative feedback
OVARY
• Follicle development
• Inhibin
• Estradiol
• Ovulation
• Corpus luteum
Progesterone
Before day 10
After day 10
KEY
Stimulation
Inhibition
Secondary Sex characteristics
Reproductive
System
Stimulation of endometrial growth and secretion
ANTERIOR LOBE OF PITUITARY GLAND
The Gonads: Ovaries

13. Male Sex Hormones Responses to Testosterone in Males
Integumentary System
Terminal hairs on the face and chest, axillae and genital area
Adipose tissues respond differently to testosterone than to estrogens
Skeletal System
Muscular System
Nervous System
Cardiovascular System
Accelerates bone deposition and skeletal growth
Promotes 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 blood volume and the hematocrit.
Respiratory System
Reproductive System
Stimulates disproportionate growth of the larynx Thickening and lengthening of the vocal cords
Gradual deepening of the voice
Development of the accessory reproductive glands Helps promote spermatogenesis.

14. The Gonads: Testes TESTES GnRH HYPOTHALAMUS LH FSH Inhibin
Negative feedback
Released relatively
steady.
ANTERIOR LOBE
OF THE PITUITARY
GLAND LH
FSH
Targets seminiferous
tubules.
KEY
Stimulation
Inhibition
Sustenacular Cells
Inhibin
Interstitial Cell
Testosterone
TESTES
Respond to factors
released by
developing
spermatozoa
Androgen-binding
protein (ABP) binds androgens of seminiferous tubules
Maturation of spermatids.
Spermatogenesis and
spermiogenesis.
Peripheral Effects
Nervous System
Skeletal System
Secondary sex
characteristics
Reproductive system

15. The Gonads: Testes

16. Androgen-Insensitivity Syndrome (Testicular Feminization)
Genetically male
Target cells lack receptors for testosterone
Female anatomy
no menstruation or uterus
presence of testes in abdomen

17. 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