Reproductive systems

Question 1

What temperature is found within the scrotum?

Answer 1

35.9 degrees

Question 2

How many lobules and seminiferous tubules are found within each testicle

Answer 2

250 lobules and 800 tubules

Question 3

What is the name of the dense capsule surrounding the testicles?

Answer 3

Dense layer of connective tissue called the tunica albuginea

Question 4

What is the pathway from the seminiferous tubules to the excretory duct?

Answer 4

Seminiforous tubules found within lobules, connected by straight tubules to rete testes, 20 efferent tubules connect to the epididymis, which connects to the excretory duct via the vans deferens

Question 5

What length are the seminiferous tubules and how much sperm do they produce daily?

Answer 5

80cm in length and 1/2 a billion sperm daily

Question 6

What is the process by which spermatocytes are ultimately formed from germ cells?

Answer 6

Germ cells are found in the outermost layer of the tubule. Primordial germ cell in the outermost layer (diploid spermatogonia) undergoes a mitotic division to produce primary spermatocytes (diploid), this undergoes a meiotic division to produce two secondary spermatocytes (haploid), which then undergo a second meiotic division to produce four spermatids (haploid), these then form the mature sperm (haploid spermatozoa)

Question 7

What are sertoli cells and what is their function?

Answer 7

1) Have an important function as a regulator in the maintenance of the blood-testis barrier. 2)Transport of materials across the Sertoli cells is tightly regulated which creates a stable environment for sperm.
3) The germ cells sit within invaginations of Sertoli cell cytoplasm, where is provides nutrition and chemical stimulation for spermatogenesis.

Question 8

What is the function and location of Leydig cells?

Answer 8

Surrounding connective tissue of seminiferous tubules - they produce testosterone.

Question 9

What is the structure of a spermatocyte?

Answer 9

Spermatocytes are particularly specialised due to their function in fertilisation of the ovum. They don’t contain specialised structures such as ER, Golgi apparatus or any glycogen or energy reserves therefore it is paramount that they absorb necessary nutrients from the surrounding fluid. Anatomically they are composed of a head with superiorly has an acrosome containing enzymes which help to penetrate the egg. Beneath this is the round nucleus. Under this is the mid-piece which is abundant in mitochondria to produce energy. They also have a flagellum tail which allows them to move. When the spermatocytes leave the seminiferous tubules, they are still functionally immature and incapable of coordinated locomotion and are not yet capable of fertilising the egg.

Question 10

What is the structure and function of the epididymis?

Answer 10

The epididymis is the coiled structure that connects the tubules to the vans deferens. Its role is to store the spermatozoa and facilitate their maturation, although when found here they are still immobile. They also recycle damaged sperm and have a role in monitoring and adjusting the composition of tubular fluid. The tubule within the epididymis is almost 7m in length highlighting the degree in which it is coiled. Smooth muscle is found on the outside which carries out peristaltic contractions facilitating movement of the sperm. Beneath this the epididymis is lined with pseudostratified columnar epithelium which contain sterocilia found innermost of the sperm containing lumen.

Question 11

What is the structure and function of the vans deferens?

Answer 11

It has a length of between 40-45cm. It ascends into the abdominopelvic cavity through a structure called the spermatic cord, where it enters the superior aspect of the prostate on the posterior surface of the bladder. The vans deferens is lined with columnar epithelium which contain tiny stereocilia. Its expanded distal end is termed the ampulla of vas. The wall is composed of typically 3 layers of smooth muscle, the contraction of which moves spermatozoa from the epididymis to the urethra during ejaculation. The ductus deferens can store the sperm for several months before it would be recycled.

Question 12

What are the percentage components of sperm fluid and its origin?

Answer 12

1) 5% fluid from seminiferous tubules
2) 60% fluid from seminal vesicles
3) 30% fluid from prostate
4) 5% fluid from cowpers gland

Question 13

What is the purpose of the seminal vesicle glands?

Answer 13

Account for 60% of semen volume. These glands contain very high levels of fructose which sperm convert to ATP for energy, allowing their flagella to beat as they develop a degree of motility. The ducts from these vesicles join the vans deferens to form the ejaculatory duct which ultimately joins the prostatic urethra.

Question 14

What is the function of the prostate?

Answer 14

The prostate accounts for 30% of seminal fluid. It is a small muscular organ encircling the prostatic urethra which produces a weakly acidic and milky thin fluid

Question 15

What is the function of Cowper’s gland?

Answer 15

The bulbourethral gland (cowper’s gland) only accounts for 5% of seminal fluid volume. This gland empties its contents into the penile urethra directly, secreting a thick alkaline mucus which provides lubrication for the glands penis and neutralises acids found in the urethra.

Question 16

What is an anatomical description of the female reproductive system?

Answer 16

It contains its germ cells within the ovary which is connected by a fallopian tube to the body of the uterus, leading into this is the cervix then the vagina which leads to the exterior of the vagina. Beneath the corpus of the uterus is the urinary bladder which leads superficially to the urethra, anterior to this is the symphysis bone, beneath which the clitoris is found. The system can be thought of as two fallopian tubes which leads into the uterus. The fundus is found at the top of the body, and the isthmus either side. The two sides touch forming the internal and external os, between which is a small space called the cervical canal – this structure forms the cervix which lies superiorly to the vagina. The most important structure arguably in this system is the ovary. It has an outermost layer of dense connective tissue called tunica albuginea – similar to the testes. The structure can be divided into a cortex and a medulla. Within the cortex oocyte and follicular development occurs and hormones are secreted, while the medulla is a loose connective tissue containing loose connective tissue and blood vessels from hilum.

Question 17

What is the number of viable ovum in a female and how does this number arise?

Answer 17

Oogonia will complete their mitotic divisions prior to birth and approx. 2 million will be present at this time, by puberty this number declines to approx. 400 thousand. The rest degenerate in a process known as atresia. Ultimately approximately 450 will be liberated for potential fertilisation

Question 18

What is the name of the process of egg degeneration?

Answer 18

Atresia

Question 19

What is the number of primary oocytes present at birth and then at puberty?

Answer 19

2 million which declines to 400 thousand

Question 20

Where are female gametes produced?

Answer 20

Ovarian follicles

Question 21

What hormone triggers the start of the ovarian cycle

Answer 21

FSH

Question 22

Wha is the structure of the primary follicle?

Answer 22

The structure of a primary follicle contains the primary oocyte centrally, surrounded immediately by the zona pellucida (a glycoprotein layer) which is then surrounded by several layers of granulosa cells. The purpose of the granulosa is to provide nutrition to the primary oocyte.

Question 23

What does the granulosa on a primary follicle do?

Answer 23

Provides nutrition to the primary oocyte

Question 24

What happens during the formation of a secondary follicle?

Answer 24

After formation of the primary oocyte only a select number will progress to the secondary follicle stage. At this stage the zona granulosa (follicular wall) will thicken and the cell will secrete small amounts of fluid forming the follicular antrum. 8-10 days after the ovarian cycle starts the ovaries will only contain a single secondary follicle containing a primary oocyte that is destined for further development.

Question 25

What are theca cells?

Answer 25

Theca cells are a group of endocrine cells that make up the surrounding connective tissue which surround the secondary follicles. Theca externa cells are found on the outermost layer and the theca interna found deeper to this have a role in progesterone and oestrogen secretion.

Question 26

What is a Graafian follicle?

Answer 26

A Graffian follicle is the tertiary follicle which develops by day 10-14 in the ovarian cycle. It is approx. 1.5cm in diameter and stretches over the ovarian wall which creates a prominent bulge on the ovarian surface. The oocyte surrounded by the corona radiata (follicular cells) project into the expanded central chamber of the fluid filled antrum.

Question 27

When does the primary oocyte become the secondary oocyte?

Answer 27

When the primary oocyte is surrounded by the corona radiata and extends into the fluid filled antrum of the tertiary follicle

Question 28

What is the corpus luteum?

Answer 28

Ovulation occurs on day 14 of the cycle and the ovarian wall ruptures, which releases the oocyte complex. Cells proliferate from an endocrine body called the corpus luteum. This yellow body synthesises progesterone which prepares the uterine wall for pregnancy.

Question 29

What is the corpus albicans?

Answer 29

In the case where pregnancy does not occur this structure degenerates approx. 12 days following ovulation. A structure called the corpus albicans, or the white body, is the name of the pale scar tissue produced when fibroblasts invade the corpus luteum.

Question 30

What is the structure and function of the fallopian tubes?

Answer 30

Fallopian tubes are the site of fertilisation. The contain highly folded mucosa which have a highly ciliated columnar epithelium which secretes lipids and glycogen to nurture the oocyte and sperm. The mucosa is surrounded by concentric layers of smooth muscle.

Question 31

What is the structure and function of the uterus?

Answer 31

The uterus contains two layers; the endometrium and the myometrium. The myometrium is found most superficially and contains 3 indistinct layers of smooth muscle. The endometrium is found deeper to this and is a glandular mucosa which consists of tubular glands. It is lined with simple columnar epithelium and contains connective tissue stroma. It is highly vascular. The endometrium is divided into the stratum functionalis and basalis. During the menstrual cycle the endometrium undergoes three phases; 1) the proliferative phase; 2) secretory; and 3) menstrual.