Physiology and health
Unit 2
• 1 Reproduction
• (a) (i)The structure and function of reproductive organs and gametes and
their role in fertilisation.
• Gamete production in the testes. The roles of seminiferous tubules,
interstitial cells, testosterone, prostate gland and seminal vesicles. Gamete
production in the ovaries to include maturation of ova and the
development of a follicle. Site of fertilisation in the oviduct and zygote
formation.
• (ii)
Testes produce sperm in the seminiferous tubules and testosterone
in the interstitial cells. The prostate gland and seminal vesicles secrete
fluids that maintain the mobility and viability of the sperm.
• The ovaries contain immature ova in various stages of development. Each
ovum is surrounded by a follicle that protects the developing ovum and
secretes hormones. Mature ova are released into the oviduct where they
may be fertilised by sperm to form a zygote.
•
Reproductive Organs and
Hormones
MALE REPRODUCTIVE SYSTEM
BLADDER
URETER
SEMINAL VESICLE
PUBIC BONE
PROSTATE GLAND
RECTUM
URETHRA
ERECTILE TISSUE
COWPER’S GLAND
VAS DEFERENS
PENIS
EPIDIDYMIS
TESTIS
SCROTUM
TESTES
SEMINIFEROUS
TUBULE
INTERSTITIAL
CELLS
Male reproductive system
• Gametes (sex cells) are produced from germline cells.
• In males, sperm are produced in seminiferous tubules found
in the testes. The surrounding interstitial cells produce the
male hormone testosterone which stimulates sperm
production.
• The prostate gland and seminal vesicles secrete fluids that
maintain the mobility and provide nutrients for the sperm.
FEMALE REPRODUCTIVE SYSTEM
OVIDUCT
ENDOMETRIUM
OVARY
CERVIX
UTERUS
VAGINA
THE OVARIES
GRAAFIAN FOLLICLE
Female reproductive system
• The ovaries contain immature ova in various stages of
development. Each ovum is surrounded by a follicle that
protects the developing ovum and secretes hormones.
Mature ova found inside Graafian follicles are released into
the oviduct where they may be fertilised by sperm to form
a zygote.
• b) Hormonal control of reproduction.
• (i) Hormonal onset of puberty.
• Pituitary gland releases follicle stimulating hormone
(FSH),luteinising hormone (LH) or interstitial cell
stimulating hormone (ICSH) via the hypothalamus
Hormonal Control
Hormones – recap!
• Hormones are chemical messengers produced by cells that
bind to receptors on the plasma membrane of other cells or
enter other cells and alter the metabolic function of these
cells.
• In response to a signal from the brain, hormones are
secreted directly into the blood by the glands that produce
and store them to travel to a specific target organ. These
glands make up what is known as the endocrine system.
Hormonal Onset of Puberty
• At puberty the hypothalamus
secretes a releaser hormone
that targets the pituitary
gland
• The pituitary gland is
stimulated to release:
• follicle stimulating hormone
(FSH)
• Luteinising hormone (LH) in
women
• Or interstitial cell stimulating
hormone (ICSH) in men
• These hormones control the
onset of puberty
Hormonal onset of puberty
• At puberty, the hypothalamus starts to produce a releaser
hormone. This stimulates the pituitary gland to start
releasing:
• Male: 1. Follicle Stimulating Hormone (FSH)
Interstitial Cell Stimulating Hormone
• Female: 1. FSH
2. Luteinising Hormone (LH)
2.
(ICSH)
• (ii) Hormonal control of sperm production.
• FSH promotes sperm production and ICSH stimulates
the production of testosterone
Gametes are
produced from germline cells. Hormones control the
onset of puberty, sperm production and the
menstrual cycle.
• The pituitary gland is stimulated to release follicle
stimulating hormone (FSH) and luteinising hormone
(LH)/interstitial cell stimulating hormone (ICSH) by a
releaser hormone produced in the hypothalamus.
Hormonal Control of Sperm
Production
Male Hormones
• FSH (follicles stimulating
hormones) promotes
spermatogenesis in
seminiferous tubules
• ICSH (Interstitial cellstimulating hormone)
stimulates interstitial cells to
produce male hormones (eg
testosterone)
• Testosterone also stimulates
sperm production and activates
the prostate gland and seminal
vesicles
NEGATIVE FEEDBACK CONTROL
• High levels of testosterone have an inhibitory effect on the pituitary gland
• Inhibits secretion of FSH and ICSH
• Thus, levels of testosterone fall
• Inhibitory effect on pituitary ceases
• FSH and ICSH secretion increases
• Levels of testosterone increase
Hormonal control of sperm production
• FSH promotes sperm production.
• ICSH stimulates the production of
testosterone which stimulates sperm
production.
• Together, FSH and ICSH exhibit negative
feedback control on the pituitary gland.
REMEMBER….
•F
•I
•T
•F
•L
•O
•P
• (iii) Hormonal control of the menstrual cycle.
Development of a follicle and the endometrium in the
uterus.
• Roles of FSH, LH, oestrogen and progesterone in the
menstrual cycle. Development of a follicle, the corpus
luteum and the endometrium. Follicular and luteal
phases. Blastocyst implantation. Negative feedback
control through pituitary gland, FSH and
progesterone, leading to menstruation.
Hormonal Control of the Menstrual Cycle
ABPI schools
• Hormones and the menstrual cycle:
• http://www.abpischools.org.uk/page/modules/hormones/horm4.cfm
?coSiteNavigation_allTopic=1
Abpi schools
• Hormones drag and drop exercise
• http://www.abpischools.org.uk/page/modules/hormones/horm2.cfm
?coSiteNavigation_allTopic=1
MENSTRUAL CYCLE
• Takes on average 28 days
• Menstruation is day 1 to 5 of
the cycle
• Endometrium then starts to
repair
• Ovulation day 14
• Endometrium thick and
spongy
• Menstruation in absence of
fertilised egg
Hormonal control of the female menstrual cycle
• The menstrual cycle takes approximately 28
days.
• The first day of menstruation where the old
endometrium (uterus lining) is shed (this lasts
approximately 5 days) is regarded as day one
of the cycle.
Menstrual Cycle – day 1-14
LH
FSH
OESTROGEN
PROGESTERONE
Hormonal control of the female menstrual cycle
• The first 14 days are called the follicular phase. FSH stimulates the
development of a follicle in the ovary and also stimulates the
production of another hormone- oestrogen - by the follicle.
• The levels of oestrogen gradually build up. This stimulates
proliferation of the endometrium, preparing it for implantation. It also
makes mucus produced by the cervix much thinner, making it easier
for sperm to penetrate.
• Peak levels of oestrogen on day 14 stimulate a surge in the secretion
of LH which triggers ovulation.
Menstrual Cycle – day 15- 28
FERTILISATION
Hormonal control of the female menstrual cycle
• Days 14 – 28 are called the luteal phase. Once the egg has been released, the
surrounding follicle develops into a corpus luteum and secretes progesterone
which promotes further development and vascularisation (formation of blood
vessels) of the endometrium, preparing it for implantation of the blastocyst
(developing embryo) in the endometrium if fertilisation has occurred.
• High levels of ovarian hormones (oestrogen and progesterone, produced by the
ovary) exhibit a negative feedback effect on the pituitary hormones ( FSH and
LH) thus reducing their release and preventing further follicles from
developing in the ovary and being released.
• If there is no pregnancy, a decrease in LH which maintains the corpus luteum
leads to degeneration of the corpus luteum. It then stops producing
progesterone which then leads to the endometrium being shed during
menstruation.
• (c) The biology of controlling fertility.
• Infertility treatments and contraception are based on the biology of fertility. Risks and
ethics associated with fertility treatments.
• (i) Fertile periods.
• Cyclical fertility in females leading to a fertile period. Continuous fertility in males.
Calculation of fertile periods and their use.
• (ii) Treatments for infertility.
• Stimulating ovulation. Ovulation stimulated by drugs that prevent the negative feedback
effect of oestrogen on FSH secretion.
• Artificial insemination. Several samples of semen are collected over a period of time. If a
partner is sterile a donor may be used.
• Intra-cytoplasmic sperm injection (ICSI).
• If mature sperm are defective or very low in number ICSI can be used — the head of the
sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.
• In vitro fertilisation (IVF).
• Surgical removal of eggs from ovaries after hormone stimulation. Incubation of zygotes
and uterine implantation. Pre-implantation genetic screening to identify genetic
disorders and chromosome abnormalities.
•
•
Biology of Fertility Control
Menstrual Cycle – day 15- 28
Fertility
• Females exhibit cyclical fertility, with a fertile period for
the few days surrounding ovulation and then otherwise
infertile. At ovulation, body temperature increases by
approx 0.5°C so the fertile period can be calculated.
• Males exhibit continuous fertility – their levels of fertility
do not change.