The reproductive system - L10

What is menarche?

A female’s first menstrual period, marking the start of their reproductive capabilities

When does menarche usually happen?

Between the age of 10 and 16, with the average being at age 12

What is menopause?

When a female’s menstrual cycle permanently ceases due to the decline of ovarian follicular activity. Typically characterised by 12 consecutive months without a period

What is the average age for menopause?

51

What are 4 factors that enable humans to be more reproductively successful than other primates?

• Biological adaptations

• Prolonged childhood

• Delayed reproduction

• Post-reproductive life

What are the benefits of biological adaptations for human reproductive success and how do these benefits contribute to reproductive success?

• Bipedalism for freeing hands

• Opposable thumbs for tool use

• Large brain size for advanced cognition

• Added life stages

• Placental efficiency

Contributions to reproductive success:

• Enhanced mobility

• Advanced toolmaking

• Problem-solving and adaptability

What are the benefits of a prolonged childhood for human reproductive success and how do these benefits contribute to reproductive success?

• Extended brain and learning development

• Social and cognitive investment

Contributions to reproductive success:

• Acquisition of survival and cultural skills

• Creativity and innovation

What are the benefits of delayed reproduction for human reproductive success and how do these benefits contribute to reproductive success?

• Reproduction after physical and mental maturity

Contribution to reproductive success:

• Improved offspring survival and care

What are the benefits of post-reproductive life for human reproductive success and how do these benefits contribute to reproductive success?

• Grandmother hypothesis (caregiving)

• Knowledge transmission

• Intergenerational support

Contributions to reproductive success:

• Increased child survival

• Stronger social cohesion

• Stability of cultural and survival practices

How long do fetus’ have undifferentiated structures for?

The first 5-6 weeks of development

At what stage to male and female structures start to differentiate in a developing fetus?

Male structures - week 7-8

Female structures - week 8-9

What happens around 7-8 weeks if a fetus is going to develop into a male?

Testosterone production begins to shrink female structures and promote growth of male structures. The testes develop

What happens around 8-9 weeks if a fetus is going to develop into a female?

Estrogen production begins to shrink male structures and promote growth of female structures. the ovaries develop

What structures are present only in a male embryo?

• Testes

• Efferent ductules

• Epididymis

• Mesonephric duct

• Seminal vesicle

What structures are present only in a female embryo?

• Ovaries

• Paramesonephric duct

• Fused paramesonephric ducts

What structures are present in both male and female embryos?

• Urinary bladder

• Urogenital sinus

What structures are present only in males at birth?

• Seminal vesicle

• Prostate gland

• Bulbourethral gland

• Ductus deferens

• Efferent ductules

• Epididymis

• Testes

• Penis

What structures are present only in females at birth?

• Uterine tube

• Ovaries

• Uterus

• Vagina

• Hymen

• Vestible

What structures are present in both males and females at birth?

• Urinary bladder

• Urethra

What is the seminal vesicle?

Paired glands that produce a fluid that forms sperm

What is the function of the prostate gland?

Production of a fluid that forms semen

What is the function of the ejaculatory duct?

To transport sperm and seminal fluid into the urethra for ejaculation

What is the function of the ductus deferens?

To transport sperm from the epididymis to the prostatic urethra

What is the function of the epididymis?

Storage and maturation of sperm

What is the function of the bulbourethral gland?

To lubricate the spongy urethra for the passage of sperm

What is spermatogenesis?

The production and maturation of sperm

What is the process of spermatogenesis?

1. Mitosis of a spermatogonium (diploid) to produce a primary spermatocyte (diploid)

2. DNA replication, synapsis (fusion of chromosome pairs) and tetrad formation

3. Meiosis 1 to form 2 secondary spermatocytes

4. Meiosis 2 to form 4 spermatids (haploid)

5. Spermiogenesis (physical maturation) to form spetmatoza (haploid)

How long does the whole process of spermatogenesis take?

64-72 days

What does testosterone secretion stimulate?

• Effects on the CNS

• Stimulation of bone and muscle growth

• Maintenance of accessory glands and organs

• Maintenance and establishment of male secondary sex characteristics

How is testosterone regulated?

Negative feedback

What does secretion of FSH stimulate in males?

• Secretion of inhibin

• Synthesis of androgen-binding protein (ABP)

• Stimulation of spermatogenesis and spermiogenesis

How is FSH secretion regulated?

Negative feedback by inhibin

What is the function of the uterine (fallopian) tubes?

To transport the egg from the ovaries to the uterus and they are the site of fertilisation

What is the function of the uterus?

To nurture a fertilised ovum

What is the function of the ovaries?

To produce eggs, progesterone, and estrogen

What is the ovarian cycle?

A sequence of follicular growth and development, leading to ovulation of mature oocytes and the formation of a functional corpus luteum

What is the uterine cycle?

The cyclic changes that occur in the lining of the uterus (endometrium) during the menstrual cycle

When is the follicular phase of the ovarian cycle and what happens during it?

Day 1-14 - the maturation of ovarian follicles, preparing them for release during ovulation

When is the luteal phase of the ovarian cycle and what happens during it?

Day 14-28 - the body prepares for potential pregnancy by thickening the uterine lining, driven by an increase in progesterone levels. If the egg is not fertilised, hormone levels decline to initiate menstruation

When is the menses phase of the uterine cycle and what happens during it?

Day 1-7 - the lining of the uterus sheds, causing menstrual bleeding. This occurs because the egg has not been fertilised and so the prepared endometrium (uterine lining) is not needed

When is the proliferate phase of the uterine cycle and what happens during it?

Day 8-14 - the endometrium proliferates (cells multiply and spread) to form a new layer of endometrium

When is the secretory phase of the uterine cycle and what happens during it?

Day 15-28 - the endometrium prepares for potential implantation of a fertilised egg. Progesterone stimulates changes in the endometrium including thickening, increased vascularity, and nutrient secretion by endometrial glands

How do levels of progesterone, estrogens, and inhibin change throughout the ovarian cycle?

Progesterone - Stays relatively stable at a low level throughout the follicular phase. Increases quickly at the start of the luteal phase to peak and then dip then peak again before decreasing back to a low level before the end of the luteal phase

Estrogens - A small peak at the start of the follicular phase, then a continued gradual increase to a larger peak at the end of the follicular phase, then a rapid decrease at the start of the luteal phase. It then peaks as progesterone peaks before returning to a low level before the end of the luteal phase

Inhibin - Stays relatively constant at a low level for most of the follicular phase with a small peak at the end of the follicular phase. It then increases to a larger peak when progesterone peaks for the second time in the luteal phase before returning to a low level before the end of the luteal phase

What effect does secretion of FSH have on developing follicles?

• Secretion of inhibin

• Secretion of estrogens

What effect does secretion of estrogen have?

• Effect on the CNS

• Stimulation of bone and muscle growth

• Establishment and maintenance of female secondary sex characteristics

• Maintenance of accessory glands and organs

• Stimulation of endometrial growth and secretion

• Secretion of progesterone by the corpus luteum

How is estrogen regulated?

Negative feedback by inhibin

What does secretion of LH cause?

Secretion of progesterone by the corpus luteum

What does progesterone cause?

Stimulation of endometrial growth and secretion

How is progesterone regulated?

Negative feedback

What influences offspring fertility for female offspring?

• Maternal health

• Epigenetic programming

Describe the development of:

1. Lymphoid immune system

2. Brain development

3. General growth

4. Genital/reproduction

1. There is a quick increase in development to 45% at age 2 and then a bit of a plateau before a rapid increase to 200% by age 12. There is then a gradual decrease to 100% by age 20

2. There is a rapid increase to 60% by age 3 before a more gradual increase to 100% by age 10

3. There is a gradual increase to 40% by age 5 before a slow increase to 60% by age 14 and then a faster increase to 100% by age 20

4. There is an initial increase to 5% by age 2 and then no significant increase until age 10 where development occurs at an increasingly high rate up to 100% by age 20

Describe the height growth rate for:

1. Girls

2. Boys

1. An initial rapid decrease from 14cm/year at age 1 to 9cm/year by age 2 then a gradual decrease to 6cm/year by age 9. There is then a rapid increase (growth spurt) up to 9cm/year at age 12 and then a rapid decline to 1cm/year by age 15

2. An initial rapid decrease from 14cm/year at age 1 to 9cm/year by age 2 then a gradual decrease to 5cm/year by age 12. There is then a rapid increase (growth spurt) up to 11cm/year at age 14 and then a rapid decline to 1cm/year by age 18

Why is there a high mortality rate for both mother and baby when girls are pregnant before having a fully developed pelvis?

• There is no pelvic growth spurt, so it takes a long time for it to reach its full mature size

• The birth canal doesn’t go through a growth spurt, so it takes a long time to develop