Reproduction

Question 1

Briefly describe the strcuture male reproductive system

Answer 1

-Male gonads consist of two testicles (or testes), where male gametes (spermatozoa or sperm) are produced
-Held and supported in a skin-covered pouch (scrotum)
-Scrotum is divided internall into 2 sacs (each containing a single testis)

Question 2

What temperature is ideal for the production of spermatozoa?

Answer 2

2°C lower than normal body temp.

Question 3

What enables the testes to maintain an average temperature that is 2°C lower than body temperature?

Answer 3

-The testes lie in the scrotum, outside the body cavity
-Muscle fibres in the wall of the scrotum contract and relax to move the testes closer or futher away from the body to regulate temp.

Question 4

What is each testis divided into? What are they filled with?

Answer 4

Lobules, filled with seminiferous tubules. They eventually join into ducts, which leave the testis and enter the epididymis.

Question 5

What does the seminiferous tubules in the testes do?

Answer 5

Lined with cells that produce the male gametes (sperm)

Question 6

What is between the seminiferous tubules?

Answer 6

Clusters of interstitial cells

Question 7

What is the epididymis?

Answer 7

A highly folded tuble that fits against the rear surface of each testis. Sperm from the testes enter the tubule of the epididymis where they are stored for up to a month while they mature. The tubule of the epididymis continues to become the vas deferens (or sperm duct), which carries the sperm away from the testes.

Question 8

State the route that the vas deferens takes?

Answer 8

Extends upwards from the testis, passes into the abdominal cavity and crosses the upper surface of the bladder. It then turns downards, looping behind the bladder. Under the bladder, the two vasa deferentia (one from each testis) join the urethra, which runs along the bladder, through the penis to the exterior.

Question 9

What is the role of the urethra during ejactulation?

Answer 9

It is a duct for transporting both urine and sperm.

Question 10

Semen is a mixture of secretion from three glands. What are these glands?

Answer 10

-The seminal vesicles
-The prostate gland
-The bulbourethral gland

Question 11

In females, which organs are considered the gonads?

Answer 11

The two ovaries

Question 12

Where are female gametes (ova) produced?

Answer 12

The ovaries

Question 13

What are female gametes called?

Answer 13

Ova (or eggs)

Question 14

Describe the structure of each ovary (shape, length, location)

Answer 14

-Almond-shaped gland
-Approx. 3cm in length
-Located completely within the body
-One on each side of the abdominal cavity supported by ligaments

Question 15

What tissue is each ovary composed of?

Answer 15

A mass of connective tissue (stroma)

Question 16

What surrounds the stroma in each ovary?

Answer 16

Numerous germ cells

Question 17

How is each germ cell enclosed in the ovaries?

Answer 17

In a follicle

Question 18

What is the state of follicles in the ovaries at any one time?

Answer 18

At any one time there are numerous follicles in various stage of development.

Question 19

What happens as a follice matures?

Answer 19

It moves to the surface of the ovary and ruptures. The egg is expelled into the funnel-like opening of the uterine tube. The egg is then carried down the uterine tube (fallopian tubes) from the ovary to the uterus.

Question 20

What enables the egg to move out of the ovary?

Answer 20

The funnel-like opening near the ovary is fringed with finger-like projection that appear to just touch the surface of the ovary (fimbriae). The fimbriae help guide the egg into the uterine tube.

Question 21

What is the uterine tube lined with that enables the movement of an egg?

Answer 21

Cilia, whose moevemnt carries the egg towards the uterus.
Contaction of smooth muscles in the wall also aid this movement of the egg.

Question 22

Where is the uterus situated?

Answer 22

Behind the urinary bladder and in front of the rectum.

Question 23

What is the wall of the uterus mostly made of?

Answer 23

Smooth muscle, with a soft mucous membrane (endometrium).

Question 24

What is at the lower end of the uterus?

Answer 24

The cervix

Question 25

Where does the cervix lead to?

Answer 25

Into the vagina

Question 26

What is the vagina?

Answer 26

A canal leading to outside of the body. It recieves the penis of the male during sexual interourse and enlarges to form the birth canal during childbirth.

Question 27

Where does the vagina open to?

Answer 27

The exterior in a region termed the vulva, which is made up of external genital organs of the female.

Question 28

What are the two types of gametogensis?

Answer 28

-Formation of spermatozoa in the tesis is called spermatogenesis -Formation of the ova in the ovary is called oogenesis

Question 29

Where does spermatogenesis occur?

Answer 29

Inside the seminiferous tubules of each testis

Question 30

What does spermatogenesis result in?

Answer 30

Results in 4 spermatozoa (sperm) from each spermatogonium

Question 31

How long does spermatogenesis take?

Answer 31

approx. 72 days, continuously after puberty

Question 32

What is a sperm made up of?

Answer 32

A head, neck, middle and tail

Question 33

What does the head of the sperm consist of?

Answer 33

Contains almost entirely of the nuclear material, with a fluid-filled vesicle at its tip (acrosome)

Question 34

What does the nuclear material in the head of sperm consist of?

Answer 34

Enzymes which break down cells surrounding the egg so fertilisation can occur

Question 35

Where does the neck lay on sperm?

Answer 35

Between the head and the middle piece

Question 36

What does the middle piece of sperm contain?

Answer 36

The mitochondira, where respiration takes place to provide the sperm with energy for movement, Around the mitochondria is a thin layer of cytoplasm.

Question 37

Why do sperm have short survival periods? Where do they recieve their nourishement?

Answer 37

Because they have so little cytoplasm. They receive their nourishment from the semen in which they are suspended.

Question 38

What is the purpose of the tail on sperm?

Answer 38

Capable of contractile motions to propel the cell foward

Question 39

Where does oogenesis occur?

Answer 39

In the ovaries

Question 40

Describe the sequence of oogenesis

Answer 40

1. Oogonium form primary oocytes prior to birth 2. After puberty, each primary oocyte completes its development to a secondary oocyte and up to 3 polar bodies 3. The secondary oocyte is released during ovulation, completing meisosis if it is fertilised

Question 41

The pituitary gland is an important endocrine gland associated with the reproductive system. Where is it located?

Answer 41

A small organ lying in a pit in the bone below the brain and above the roof of the mouth.

Question 42

What are the two hormones secreted by the pituitary gland that affect the gonads?

Answer 42

-Follicle-stimulating hormone (FSH) -Luteinising hormone (LH)

Question 43

What does follicle-stimulating hormone (FSH) do for females?

Answer 43

Stimulates the development and maturation of the ovarian follicle in females. Durings its development, the ovarian follicle secretes oestrogen. Secretion of FSH is reduced as the level of oestrogen increases in the blood.

Question 44

What else besides FSH and LH does the pituitary gland release in relation to reproductive hormones?

Answer 44

-Prolactin (important in the preparation and maintenance of milk production) -Oxytocin (causes uterine contractions, amongst other effects)

Question 45

What does luteinising hormone (LH) do for females?

Answer 45

Promotes the final maturation of the ovarian follicle, ovulation, and the formation of the corpus luteum. The corpus luteum secretes progesterone as well as oestrogens. There is a reduction in production of LH as the lvele of progesterone in the blood increases.

Question 46

What does luteinising hormone (LH) do for maless?

Answer 46

Stimulates cells in the testes to secrete the hormone testosterone, which is important for the development of immature sperm cells into mature spermatozoa

Question 47

What does follicle-stimulating hormone (FSH) do for males?

Answer 47

Stimulates the epithelial tissue of the seminiferous tubules in the testes to produce sperm.

Question 48

What is the ovarian cycle?

Answer 48

A series of events that take place within the ovaries. It includes the maturation of an egg and its release into a uterine tube. Associated with these events are the development of follicles in the ovary and the formation of the corpus luteum. The average length of the cyle is 28 days.

Question 49

Outline the ovarian cycle

Answer 49

-At ovulation, the mature follicle bursts and expels the oocyte, which is gradually swept down the uterine tube toward the uterus (by cilia) -Following ovulation, the corpus luteum is formed, which secretes oestrogen and progesterone (influences the development of the lining of the uterus, preparing for implantation if fertilisation occurs). Also inhibits the release of FSH and LH which prevent other follicles from maturing -If fertilisation does not occur, the corpus luteum reaches its max. development and beings to degenerate (8-10 days), menstuation occurs, new cycle begins -If fertilisation does occur, the corpus luteum continues to develop and the ovarian cycle ceases

Question 50

What is the fole of Progesterone?

Answer 50

Influence the development of the lining of the uterus, perparing for implantation IF fertilisation occurs.

Question 51

What hormone maintains the corpus luteum?

Answer 51

Human Chorionic Gonadotropin (HCG), a hormone produced by the developing placenta in a pregnant woman

Question 52

What is the menstrual cycle?

Answer 52

A series of changes that result in the uterine lining (the endomertrium) becoming prepared in the event that fertilisation does occur.

Question 53

Outline the menstrual cycle

Answer 53

-While the follicle is maturing in the ovarian cycle, progesterone causes the enodmetrium of the uterus to become thicker and softer -Increase in number of blood vessls and musuc-sexreting glands -After ovulation the endometrium continues to thicken, and glands within it begin to secrete a water mucus rich in glycogen -If the egg is not fertilised by a sperm, the corpus luteum degenerates reducing the amount of progesterone, which results in its breakdown - about 14 days after ovulation, blood from broken-down capillaries, mucous secretions and cell debris from the uterine lining ar lost through the vagine -Often takes place over several days

Question 54

State the major stages of the menstrual cycle and their average duration

Answer 54

Menstruation 1-4 days (uterine bleeding, shredding of the endometrium) Preovulation 5-12 days (endometrial repair begins, development of ovarian follice, uterine lining gradually thickens) Ovulation 13-15 days (rupture of mature follice (releasing egg)) Secretion 16-20 days (secretion of water mucus by gland of endometrium, crevix and uterine tubes; movement and breakdwon of unfertilised egg; development of corpus luteum) Premenstruation 21-28 days (degeneration of corpus luteum; deterioration of endometrium)