Reproductive system 2

Question 1

What are some of the major structures in the male testes? And their general function

Answer 1

Seminiferous tubules:
- Hundreds of highly coiled tubes (over 2’ long) packed into tunica albuginea
- Site of spermatogenesis (1500/s/testicle)
- Lot of cell proliferation going on in both mitosis and meiosis.
Rete testis:
- Collect sperm from seminiferous tubules
Efferent ducts:
- Carry sperm to epididymis
Epididymis
- Coiled tube (4-5m) alongside of testis
Sperm storage and maturation

Question 2

Describe the pathway of sperm through all these structures.

Answer 2

Within seminiferous tubules, there is lumen in which sperm is collected -> Sperm then moves up and is collected into the rete testis -> moves into head of epididymis -> they’re modified and altered and move out through ductus deferens.

Question 3

Where do sperm gain their motility?

Answer 3

Head of epididymis.

Question 4

Why are testis outside the body?

Answer 4

Testis are outside the body temperature to maintain its optimal temperature.

There’s a lot of vascularisation to help control testis temperature.

Question 5

What is the site of Leydig cells?

Answer 5

Testes are site of Leydig cells.

Question 6

What do Leydig cells produce?

Answer 6

Leydig cells produce testosterone.

Question 7

What are the actions of testosterone in a male at birth, after birth and during puberty.

Answer 7

Before birth
• Male external genitalia
• Male reproductive tract
• Descent of testes into scrotum

After birth • Testosterone secretion ceases
• Testes and remainder of reproductive system remain small and nonfunctional until puberty

Puberty
• Testosterone secretion surges
• Testes enlarge and spermatogenesis begins
• Penis and scrotum enlarge
• Accessory secretory glands enlarge to support development of semen, and begin secreting
• Development of secondary characteristics; pubic hair, facial hair, vocal cords lengthen

Question 8

Aside from the reproductive system, what else does testosterone affect?

Answer 8

Look in slide 12

Question 9

What are some of the structures in the male spermatic cord?

Answer 9

• Sperm exit the epididymis and enter the ductus (vas) deferens (thick-walled tube that travels within the spermatic cord)
  
  • The spermatic cord consists of a series of muscle and fascial layers, and carries the testicular artery and vein
  • The cord passes through the inguinal canal, which is an oblique channel through the abdominal body wall.

Question 10

What are the functions of testicular artery and vein?

Answer 10

Support spermatogenesis: support proliferation

Regulate temperature.

Question 11

How to detect prostate cancer?

Answer 11

Do a blood test. And see if there’s any of PSA in the bloodstream.

PSA is marker of blood vessel invasion by a tumour, which invades into the blood cell, into vasculature. It will release some PSA, prostate specific antigen, into bloodstream where it can be detected by blood test.

Question 12

What is the structure, location and function of seminal vesicles and prostate glands.

Answer 12

Seminal vesicles
• Paired set of organs; Posterior surface of bladder
• Joins with d. deferens to form ejaculatory duct
• Secrete a viscous fluid of fructose (sugar) and prostaglandins
• Sugars nourish sperms in the reproductive tract
• Prostaglandins dilate the cervix to allow sperm into uterine cavity and hopefully find an egg. Prostate gland
• Walnut-shaped gland inferior to bladder
• Secretes citric acid (nourishing the sperm), seminal plasmin (antibiotic that combats UTIs), and PSA (prostate-specific antigen) that liquefies semen after ejaculation

Question 13

What is the general function or urethra, and what are some components of it?

Answer 13

Tube that transports semen from ejaculatory duct
– Prostatic urethra
– Membranous urethra
– Spongy urethra

Question 14

What are the three primary erectile tissue bodies in the penis? What is their location?

Answer 14

Erectile tissues are spongy masses of tissue that contain large amounts of potential vascular space for blood engorgement.
• Corpus cavernosum (clitoris) • Paired masses on the anterior surface of the flaccid penis.
• Corpus spongiosum • Single mass surrounding urethra, posterior side of flaccid penis
• The expanded distal end is the glans, with the external urethral orifice

Question 15

What are the 3 male sexual functions? Hint: It has 3 E’s

Answer 15

• Erection
  
  • Parasympathetic nerve fibers reach the penis via pelvic splanchnic nerves
  • Dilate arteries in the penis and enable the erectile tissues to fill with blood
• Emission
  * Refers to the movement of secretions of the glands (seminal vesicles, prostate and bulbourethral), along with spermatozoa, into the prostatic urethra
• Ejaculation (Orgasm)
  * Expulsion of semen by the rhythmic contractions of the bulbospongiosus and ischiocavernosus muscles that wrap around the corpus spongiosum and corpus cavernosa, respectively. This allows semen to be ejected with enough force to move into vagina to cervix. Cervix will then be opened and then out into uterine cavity, and through fallopian tubes to find oocyte read for fertilisation.

Enter
Emoji
Effectively

Question 16

How do Spermatogonial cells become spermatids?

Answer 16

Spermatogonial stem cells will undergo mitosis and enter meiotic cycle.

Spermatocytes have undergone synthesis phase. They’ve got double amount of DNA, larger nucleus, larger in size. They’re ready to undergo meiotic divisions. This will result in round spermatids.

Spermatids have a head and compacted nuclei.
Haploid spermatozoa are developed, and these will be released into the lumen, of seminiferous tubule, and then taken up and collected into the rete testis before their progression into the epididymis.

Question 17

What are the functions of Sertoli cell?

Answer 17

• Express SRY, which is testis determining master transcription factor.
  
  • Express Anti-Müllerian hormone (AMH) - early stages of fetal life. Which helps drive regression of female reproductive tract.
  • Inhibin and activins - regulate FSH secretion after puberty. Produce hormones and factors that support stem cells. Spermatogonial stem cell population helps to ensure that spermatonial stem cell population self-renews to allow foundational set of cells to be maintained in order to support huge amount of spermatogenesis that is being produced.
  • At puberty, a man starts to produce a new set of cells, which are post-meiotic germ cells. So sertoli cells can actually form a blood-testis barrier, a barrier that stops immune system from ever seeing any of these post-meiotic germ cell and recognizing and killing them.
    To take nutrients from bloodstream and pass them up through later germ cell types that are not in contact with the vasculature.

Question 18

Half of the sperm will produced carrying X chromosome, and the other half carrying Y. How does it counteract this?

Answer 18

This could result in differences in function between X or Y sperm.
To counteract this; developing germ cells maintain sensitive (cytoplasmic) bridges, entire way through their development until just before they are released, which means if there any genes expressed from X or Y chromosomes, those products are shared with all of the developing sperm.

Question 19

What morphological changes do male germ cells undergo?

Answer 19

They form a standard look cell, nucleus, golgi, apparatus. As they go through spermatogenesis:

- They start to form a flagellum. 
- Histones that wrap around DNA are replaced by transitional proteins. Protein get huge compaction of DNA and chromatin in the head of sperm -> end up with specialised cell type. It has acrosome, derived from golgi apparatus, tightly compacted nucleus, mitochondria (concentrated in middle of sperm, that will provide energy for sperm to swim).

Question 20

Describe structure of ovaries in females, and their general function

Answer 20

Paired sex organs; site of oocyte development
• Anchored to body wall via broad ligament (sheet of peritoneum)
• Important: oestrogen synthesis

Question 21

What are the functions of oestrogen in different parts of the body?

Answer 21

Brain
Maintenance of body temperature
Aids against memory loss

Heart/liver
Regulates production of cholesterol

Bone
Preservation of bone density

Breast
Stimulates development at puberty
Preparation of glands for lactation towards end of pregnancy

Uterus
Stimulates maturation of uterine tissues
Preparation for foetal implantation

Ovary
Stimulates maturation of oocytes
Stimulates initiation of menstrual cycle

Question 22

What deficiencies do we see at menopause?

Answer 22

At menopause, we start to see a decrease in oestrogen production from ovaries -> leading to memory loss and drop in bone density.

Question 23

What are some of the main structures in the female reproductive system: External genetalia. And describe the structures of these structures, and their location (if mentioned in lectures).

Answer 23

• Mons pubis – Expanse of skin and subcutaneous tissue anterior to the pubic symphysis
• Labia majora – Paired, thickened folds of skin, sebaceous glands, connective tissue. They are related to the scrotal tissue in men.
• Labia minora – Paired, highly vascular folds with sebaceous glands and melanocytes. They are are the internal structures that help to protect the entrance into the vagina.• Clitoris – Small erectile body anterior to l. minora
  • Prepuce – Fold of labia minora covering clitoris
  • Vestibule – Potential space between labia minora
  – Urethral opening and vaginal orifice
  – Bulbs of the vestibule and greater vestibular glands

Uterine (Fallopian) Tubes
- These are directly opposite of ovaries.
• Project from uterus with infundibulum at distal end
• Fimbrae are finger-like projections from infundibulum

Uterus
• Pear-shaped, muscular organ
• Fundus is the body of the uterus
• Cervix is the inferior neck of the uterus projecting into the vagina
• Cervical os: Opening to vagina. This is acted upon by some of secretions from glands, from male reproductive system to help open that area.

Question 24

What are the three layers of the uterus: female reproductive system? What is the structure of the three layers?

Answer 24

• Perimetrium
- Peritoneum and underlying connective tissue.
• Myometrium
- Thick layer of smooth muscle (high regenerative/proliferative capacity!).
• Endometrium
Simple columnar epithelium with underlying connective tissue.

Question 25

Describe the structure of the vagina, its location and its relation with some of the other structures.

Answer 25

• Elastic tube with SM in wall lined by stratified squamous epithelium
• Lies between urinary bladder (anterior) and rectum (posterior)
• Opens into the vestibule
• Projection of cervix into vagina creates an anterior and posterior fornix

Question 26

Approximately, how many female germ cells (oocytes) in 5 weeks, 16 and 20 weeks, and at birth.

Answer 26

5 weeks of gestational age an estimated 700–1300 germ cells.

Between weeks 16 and 20, peak of an estimated 6 × 106 cells per ovary.

At birth, estimated to be ∼0.5-1 × 106 cells.

Question 27

Why do the number of germ cell decrease after weeks 16-20?

Answer 27

You want your ovarian reserve to be absolute gold standard reserve cell because those cells are produced during gestation. They’ve got to survive and be viable gametes, all the way into late 30s and early 40s. So by taking the ones that are not quite right, the number of cells decrease.

Question 28

Describe all the stages of maturation of the oocyte. Like how an oocyte develops.

Answer 28

Before birth:
Cells from the ovary surround the oocyte to form the primordial follicle. Before birth, primordial germ cells travel through the foetus or through the embryo to get to ovary, and cells of ovary will surround oocyte to form primordial follicle.

At birth:
Oocytes completely enclosed in follicular (granulosa) cells.

To puberty:
Follicle size increases due to increase in oocyte size, and number of follicular cells.

Additional cellular layers are formed (once it becomes 2-3 layers thick), which will ultimately form the theca interna and externa.
Theca cells also produce androgens that are converted into estrogens (17b-estradiol) by the aromatase enzyme produced by the granulosa cells. So there’s a biochemical interaction between granulose and theca cells to essentially produce the oestrogen produced by ovary.
As puberty approaches, continued follicular maturation requires follicle stimulating hormone (FSH), [important] produced by the pituitary. This means: those follicles, which is the oocytes and granulosa cells, that follicular maturation require follicle stimulating hormone FSH produced by the pituitary.
10 to 12 hrs before ovulation, meiosis resumes in the embryo, just as primordial germ cells colonise ovary, meiosis commenced, and then stopped. Then started at 10-12 hrs before ovulation. Many years later, at puberty, meiosis resumes.

Up to 50 follicles start the maturation process each month. One will dominate! Dominant follicle is defined around 7 days prior to ovulation.
Dominant follicle enlarges, becomes FSH-independent (it becomes independent of that FSH that all other maturing follicles need) and secretes high levels of inhibin.
Inhibin suppresses pituitary FSH production causing the remaining semi-matured follicles to degenerate - atretic follicles

Question 29

What are similarities in spermatogenesis and oogenesis?

Answer 29

As PGCs they have undergone a long journey to the gonad.

Once in the gonad, they are surrounded by:
- support cells (Sertoli/granulosa) and
- hormone-producing cells (Leydig/theca) cells.
They undergo significant maturation during their development to produce final gametes.
They are the only cell types in the body to undergo meiosis.

Production of haploid germ cells that will combine to form a new person

Question 30

Why is the size of the sperm much smaller than the size of an oocyte?

Answer 30

The sperm, with their compact nuclei carry few products into the egg (apart from their DNA and centriole).

The oocyte supplies essential proteins and mRNAs for the first few days of development until the foetal genome switches on.