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Biology Unit 4 > Sexual reproduction in humans 4.1 > Flashcards

Sexual reproduction in humans 4.1 Flashcards

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1
Q

What is the scrotum?

A

Sack outside the body which contains the testes.

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2
Q

What are the testes?

A

A series of seminiferous tubules where sperm is produced.

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3
Q

What is the vas deferens?

A

It carries sperm from the epididymis towards the penis

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4
Q

What is the epididymis used for?

A

Storage of the sperm while they become motile.

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5
Q

what is the seminal vesicle?

A

It is an accessory gland producing the majority of the semen; fructose, proteins, citric acid, potassium, phosphorus and prostaglandins.

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6
Q

What is the prostate gland?

A

An accessory gland that produces alkaline fluid containing zinc, lubrication and nutrition for sperm, helps neutralise acidic vaginal environment.

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7
Q

What is the urethra?

A

It carries urine and semen out of the body.

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8
Q

What is the penis?

A

During copulation, deposits sperm in neck of womb ie. cervix.

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9
Q

What is the ovary?

A

Gland where oogenesis occurs.

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10
Q

What do the fallopian tubes do?

A

Transports secondary oocyte then the ovum then the embryo to the uterus.

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11
Q

What is the endometrium?

A

Inner most layer of the uterus. Is a mucous membrane, which is well supplied with blood. Layer which builds up and sheds in a monthly cycle.

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12
Q

What is the vagina?

A

Where sperm deposited during sexual intercourse.

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13
Q

What is the uterus?

A

Growth of embryo - fetus. Contains placenta.

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14
Q

What is the urethra?

A

Carries urine out of the body.

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15
Q

What are the two versions of gametogenesis?

A

Spermatogenesis and oogenesis.

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16
Q

What is spermatogenesis?

A

Production of male gametes by the process of meiosis. This takes place in the seminiferous tubules.

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17
Q

In which order does spermatogenesis take place?

A

Germinal epithelium - Spermatogonium - Primary spermatocyte - secondary spermatocyte - Spermatids - Sperm cells.

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18
Q

What is the Sertoli cell?

A

A nutritive cell that provides nutrients for spermatids and spermatozoa.

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19
Q

When is the first meiotic division in spermatogenesis/

A

Primary spermatocyte - Secondary spermatocyte.

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20
Q

What is the nucleus for in the sperm cell?

A

Contains genetic information. Haploid, contains 23 chromosomes.

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21
Q

What is the centriole for in the sperm cell?

A

Creates spindle fibres in meiosis, in a mature cell it migrates to pole to aid flagella formation.

22
Q

What is the acrosome for in the sperm cell?

A

Contains hydrolase to digest coronaradiata and zonapellusida.

23
Q

What are the leydig cells?

A

Located between the seminiferous tubules. When stimulated by a hormone from the pituitary gland called LH, the Leydig cells secrete testosterone.

24
Q

What does testosterone stimulate?

A

1: The development of male secondary sexual characteristics
2: The production of spermatozoa.

25
Q

Why is the production of haploid gametes essential?

A

So that as a result of fertilization, the diploid condition is restored.

26
Q

What is oogenesis?

A

Produces the female gametes. Cells in the germinal epithelium of the ovary divide by mitosis to produce oogonia. These then divide by meiosis to produce the female gametes.

27
Q

When is the ovum formed?

A

Only when the sperm has entered, fused with oocyte cell membrane and meiosis 2 completed.

28
Q

What are the products of the first meiotic division in oogenesis?

A

Secondary oocyte and first polar body.

29
Q

In what order does oogenesis occur?

A

Germinal epithelium - oogonia - primary oocyte - secondary oocyte + first polar body - Ovum + second polar body.

30
Q

What happens when the secondary oocyte and the first polar body are formed?

A

Meiosis is arrested at metaphase II - a secondary oocyte is released at ovulation.

31
Q

When is the second meiotic division completed in oogenesis?

A

Only completed at entry of a single sperm cell.

32
Q

What needs to happen to the sperm before fertilisation can take place?

A

Sperm need to be transferred from the sperm ducts to the fallopian tubes.

33
Q

Where does fertilisation take place?

A

In the fallopian tubes.

34
Q

What is capacitaion?

A

The membrane covering the front of a sperm cell becomes thinner.

35
Q

Describe fertilization?

A

1: The membrane covering the front of a sperm cell becomes thinner.
2: Membrane covering the acrosome breaks open and the acrosome releases hydrolase enzymes - these digest the corona radiata and the zona pellucida.
3: The acrosome then inverts and forms a needle like process at the front end of the sperm cell. The acrosome process binds to receptors on the vitelline layer.
4: This causes the cell membranes of the sperm and oocyte to fuse.
5: The nucleus enters the oocyte.
6: Cortical reaction results through exocytosis of the cortical granules in the formation of a fertilisation membrane (hardening and thickening of vitelline layer) that prevents the entry of further sperm cells.
Entry of sperm also triggers meiosis II to resume - the ovum nucleus is formed and almost immediately fuses with the sperm nucleus to form a new cell called the zygote.

36
Q

What is the cleavage period?

A

Following formation of zygote, new diploid cell must undergo mitotic divisions to increase cell number. No growth in size in this period.

37
Q

How is the blastocyst formed?

A

Morula divides unevenly and a blastocyst forms.

38
Q

How does the blastocyst differentiate?

A

Inner mass of cells produces an embryonic disk that will eventually form the whole of the tissues of the foetus. Two embryonic membranes also form - the chorion and the amnion. These membranes surround the foetus in a fluid filled sac for protection. Chorion also forms growths called chorionic villi that form the basis of the placenta.

39
Q

What are hormones?

A

Chemical messengers produced by endocrine glands.

40
Q

What does FSH do?

A

1: Stimulates the maturation of a primary follicle
2: Stimluates the ovary to secrete oestrogen.

41
Q

What does oestrogen do?

A

1: Stimulates the anterior pituitary gland to secrete LH
2: Stimulates the uterus to produce a new endometrium.
3: Inhibits the secretion of FSH by the anterior pituitary.

42
Q

What does LH do?

A

1: Causes graafian follicle to release a secondary oocyte = ovulation.
2: Stimulates the formation of a corpus luteum which secretes progesterone
3: Inhibits the secretion of oestrogen by the ovary.

43
Q

What does progesterone do?

A

1: Maintains the endometrium in preparation for implantation of a blastocyst.
2: Stimulates the secretion of oestrogen
3: Inhibits the secretion of FSH and LH.

44
Q

What happens if implantation doesn’t occur?

A

1: Corpus luteum degenerates
2: Progesterone levels decrease
3: Resulting in lower oestrogen levels
4: Endometrium breaks down
5: FSH secretion is no longer inhibited

45
Q

What happens if implantation does occur?

A

1: Placenta forms which secretes human chorionic gonadotrophin hCG which maintains the corpus luteum during pregnancy.
2: hCG therefore maintains the secretion of progesterone which stimulates the secretion of oestrogen.
3: After 8th week of pregnancy the placenta takes over the secretion of oestrogen and progesterone.

46
Q

What happens at the end of gestation?

A

Levels of oestrogen and progesterone fall - this triggers production of prolactin by anterior pituitary gland. This prepares the mammary glands to produce milk. It also stimulates the secretion of oxytocin from the posterior pituitary gland that stimulates the muscles of the uterus to contract during birth to force the foetus out.

47
Q

How does the placenta help towards exchange between mother and foetus’s blood?

A

1:Inter-villous spaces containing the mother’s blood surround the chorionic villi. Chorionic villus cells have microvilli, giving a large are of contact with the mother’s blood for maximum exchange.
2: Distance between embryos and mothers blood is short to allow diffusion to operate effectively.
3: Concentration gradient between the two circulations is maintained by a counter-current flow, enhancing exchange efficiency.

48
Q

What is the physical barrier between the foetal and maternal circulation for?

A

1: Protects the fragile, foetal capillaries from damage by the higher blood pressure of the mother.
2: Protects the developing foetus from changes in maternal blood pressure.

49
Q

How does the placenta provide passive immunity to the foetus?

A

Maternal antibodies cross the placenta and attack pathogens but do not attack the foetal cells, even though they carry the father’s antigens, which are different from the mother’s.

50
Q

How does the placenta provide protection from the mother’s immune system?

A

Mother does not make an immune response against the foetus or placenta, even though they contain foreign genes, i.e from the father. One reason is that the cells of the chorionic villi fuse so there are no spaces between them, making a syctitium.

Biology Unit 4 (8 decks)

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