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Chapter 10

PSYB64H3 Chapter Notes - Chapter 10: Male Reproductive System, Orgasm, Progestin

Course Code
Janelle Leboutillier

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The term sex is used to refer to biological sex
Gender is used for social, learned and personal aspects
An individual’s sex begins with sex chromosomes inherited from 2 parents
Mothers provide X chromosomes (individual with x chromo. Develop into females)
Fathers provide both x and y chromo. They determine the child’s sex. Individuals with y
chromo. Develop into males.
The sex chromo. (23rd pair)Comes along with 22 other pairs of chromo.
Karyotype is a profile of chromosome number and appearance in the nucleus of the cell as
seen under a microscope.
The 23 pairs of chromo. Are found in the nuclei of body cells in humans except the RBC
(they have no DNA), sperm cells and eggs cells (they only contain one copy from each pair
of chromo.)
Mosaic karyotype means that a single individual has cells with differing complements of
Sex chromosomes abnormalities
Down syndrome occurs when an individual has 3 copies of the 21st chromo.
Having a third copy of the sex chromo. Has mild effects, people with this do not usually get
Turner syndrome is when a person receives a single X chromosome instead of XY or XX.
People with turner syndrome have normal female appearance and genitalia but are usually
infertile (abnormally developing ovaries).
Klinefelter syndrome is a condition in males caused by an XXY genotype characterized by
frequent problems with fertility, secondary characteristics and verbal skills. It is the most
common sex chromosome genetic disability
People with klinefelter are typically male, they require hormone therapy at puberty to prevent
breast development and promote development of secondary male characteristics. They are
usually left handed.
47,XYY people with this are males. They appear to be physically within typical limits, they
are usually taller and leaner, have acne and have risk for minor physical abnormalities in the
eyes, chest and elbow. They are usually fertile but more likely to produce sperm cells with
abnormal sex chromo
3 Stages of prenatal development
-Development of the Gonads
-Differentiation of internal organs
-Development of external genitalia
All three processes occur concurrently to produce an unambiguous male or female.
In rare conditions intersex occurs. A condition in which elements of both male and female
development occur in the same fetus
Development of Gonads- Up until the sixth week both female and male embryos have
identical primordial gonads. They could develop into ovaries or testes
At the 6th week a gene on the short arm of the Y chromosome(sex determining region of the
Y chromosome or SRY) encodes testis determining factor and is expressed in the male
The testis determining factor is a protein encoded by the SRY gene on the Y chromosome
that turns primordial gonads to testes.
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The lack of SRY gene in female embryo guide the development of primordial gonad into
Differentiation of internal organs-both male and female embryos posses a male wolffian and
mullerian system until the third month into development.
Wolffian system he internal system that develops into seminal vesicles, vas deferens and
prostate gland in males
Mullerian system the internal system that develops into fallopian tube uterus and the upper
two thirds of the virgina in the absence of the of anti mullerian hormone in females
The male’s new testes secretes 2 hormones testosterone(develops and maintains male
characteristics) and anti-mullerian hormone (degradation of mullerian system)
In the female embryo the ovaries are not active. The anti mullerian is not present and the
androgen (testosterone) is also absent so the wolffian system regresses.
Androgen insensitivity syndrome (AIS) a condition where a genetic male lacks androgen
receptors and this leads to the development of female external genitalia and typical female
gender identity and sexual behaviour.
In AIS defective gene produces abnormal androgen receptors and as a result the fetuses
tissue are blind to the presence of androgen
Fetuses with AIS have XY genotype and testes that remain undescended within the
abdomen. The testes release the androgen and anti mullerian but the lack of functional
androgen system prevents the development of a wolferian system. But since the the anti
mullerian works fine the males does not develop the female mullerian system (internal
system that develops into fallopian tube uterus and the upper two thirds of the vigina) They
develop a shalow vigina. The external appearance of an AIS individual is typically female
AIS provides a clear view of the difference between chromosomal sex and gender
identity(The sense of being male or female, independent of genetic sex or appearance).
AIs individuals are genetically male but typically have female appearances and gender
Development of external genitalia- This follows after the differentiation of gonads at the sixth
week of conception.
The male external genitalia includes penis and scrotum.
Female external genitalia includes labia,clitoris and outer part of the vagina.
Prader scale is used to access the relative masculinity of the external genitalia of newborns.
Hypospadia is a situation where the urethra of the male is not properly position relative to the
No hormonal activity is required to develop female external genitalia
For males, an androgen called 5-alpha-dihydrotestosterone must be recognized by the
receptor sites for the male E. genitalia to develop properly.
5-alpha-dihydrotestosterone is a androgen secreted by the testes that masculinizes the
external genitalia. It is produced by a rxn between testosterone from the testes and an
enzyme 5-alpha-reductase.
Congenital adrenal hyperplasia (CAH) is a condition in which a fetus is exposed to higher
than normal androgens resulting in masculinization of external genitalia and some cognitive
behaviours in females.
CAH is a recessive heritable condition where the fetus’s adrenal glands release elevated
levels of androgen during the second trimester of their pregnancy.
Males with CAH show few observable effects related to sexual development.
Females with CAH are usually born with ambiguous external genitalia.
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Development at puberty
The average age of puberty has dropped from about 16 to 12
Exposure to compounds similar to female hormones in meats, dairy,shampoo and
insecticides might trigger puberty.
All edible tissues from animals contain a type of estrogen or estradiol
Estrogen is a steroid hormone that develops and maintains typically female characteristics
Estradiol is an estrogen hormone synthesized primarily in the ovaries
Hormone changes at puberty
At the onset of puberty gonadotropin-releasing hormone (GnRH) is released by the
GnRH is a hormone released by the hypothalamus that stimulates the release of luteinizing
hormone (LH) and follicle stimulating hormone (FSH) by the anterior pituitary gland.
FSH is hormone released by the anterior pituitary that stimulates the development of eggs in
the ovaries and sperm in the testes.
LH is hormone released by the anterior pituitary that signals the males testes to produce
testosterone and regulates the menstrual cycle in females.
Testes produce small amounts of estrogen including estradiol while ovaries produce small
amounts of androgens including testosterone.
In males the burst of additional androgens stimulates secondary male characteristics
In females estradiol stimulates secondary female characteristics
5-alpha-reductase deficiency affects the maturation of male external genitalia.
5-alpha-reductase deficiency is a rare condition in which a child is born with ambiguous
genitalia but develops male secondary characteristics at puberty.
Individuals born without sufficient 5-alpha-reductase are typically raised as females even
though they have internal male organs
Gender dysphoria is distress that may accompany the incongruence between one’s
experienced and assigned gender.
Sex differences in hormones, brain structure and behaviour
Sex hormones are classified as steroids, chemicals that are synthesized from the cholesterol
in the gonads and in lesser amounts in the adrenal glands, brain bone and fat cells.
Sex hormones organize circuits in the brain that differ according to sex in prenatal and early
postnatal stages.
Organization produces permanent changes in biological structure
Organization is the permanent effects of sex hormones on body structure
After organization activation occurs.
Activation by hormones is reversible, although the effects by hormones are constrained by
the organizational effects that occurred first
Organization during development
Sex hormones play important roles at 3 points in human development
-Prenatal development (6-24 weeks)
-A period beginning shortly before birth and extending to the age of 6 to 12 months
-At puberty
For males during these times they have especially high testosterone levels
During the first part of the prenatal organizational period testosterone contributes to the
development of male reproductive system and influences the both the rep. System and brain
during the latter part which contains androgen receptors.
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