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Human Bio > Chapter 12 > Flashcards

Chapter 12 Flashcards

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Biology 101 flashcards
1
Q

What causes an ejaculation

A

sexual stimulation of the penis, rhythmic contractions of the epididymis, the vas deferens, prostate gland

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2
Q

List factors that contribute to smoother entry of the penis during sexual intercourse

A

semen secreted from the seminal vesicle, prostate gland and bulbourethral gland, and mucus secreted by glands near the opening of the cervix and opening of the vagina.

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3
Q

Why are so many sperm needed to fertilize one egg

A

Sperm death rate is high so only a few thousand reach the fallopian tubes. Enzymes in sperm are needed in large amounts to loosen the corona radiata and penetrate the egg.

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4
Q

Where is the optimal location of fertilization

A

one third the way down the fallopian tubes

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5
Q

Name and briefly describe the two layers surrounding the secondary oocyte at ovulation

A

The outer corona radiata consists of follicle cells held together by cementing materials that contain acid.
The inner zona pellucida is a glycoprotein matrix surrounding the plasma membrane of the oocyte.

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6
Q

Explain how one sperm comes into contact with an egg

A

Thousands of sperm release enzymes to loosen the cells of the corona radiata until a sperm can move through it and penetrate the egg. Th sperm encounters the zona pellucida where an acrosomal reaction occurs. Digestive enzymes of the acrosome break down the glycoprotein matrix to access the plasma membrane. When the plasma membrane of the egg and sperm fuse, the nucleus of the sperm enters the ova. The entrance of one sperm stimulates the formation of a fertilization membrane around the egg, preventing other sperm from entering.

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7
Q

What is a blastocyst

A

A hollow ball of cells formed during early embryonic development that surround a cavity of fluid.

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8
Q

What is the inner cell mass and it’s function

A

A collection of stem cells inside a blastocyst. They will differentiate into body cells forming the early embryo.

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9
Q

What is the cleavage stage

A

A series of mitotic divisions where the volume of an egg’s cytoplasm is divided into numerous nucleated cells.

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10
Q

What is implantation and how long after blastocyst formation does this occur

A

2-3 days after formation of the blastocyst. Where the blastocyst sinks into the endometrium and becomes firmly attached to the uterus wall. The blastocyst can gain nourishment for growth by absorbing nutrients from glands and vessels of the uterine wall.

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11
Q

What is proliferation

A

Continuous mitotic divisions of stem cells

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12
Q

What can trigger stem cell differentiation

A

Cell’s genes, chemicals secreted by other cells, physical contact with neighboring cells and microenvironment.

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13
Q

Differentiate between totipotent, pluripotent and multipotent stem cells.

A

Totipotent - can differentiate into any type of cell necessary for embryonic development including embryonic membranes and placenta
Pluripotent - cells of the inner cell mass. Can differentiate into cells necessary for growing of the fetus itself, however not embryonic membranes or the placenta.
Multipotent - give rise to cells with specific function. Example: blood stem cells give rise to RBC, WBC and platelets.

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14
Q

Describe the primary germ layers

A

ectoderm - outermost layer, forms outer layers of body, skin, hair, nervous system
mesoderm - middle germ layer, skeleton, muscles, connective tissue, heart blood
endoderm - inner germ layer, lining digestive system, lungs, thyroid.

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15
Q

Describe the amnion

A

First fetal membrane to develop, creates cavity that secretes amniotic fluid, which protects fetus physically and acts as shock absorber, creates constant temperature and allows free movement, when amnion ruptures before childbirth, fluid releases which is water breaking

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16
Q

Describe the chorion

A

Formed from outer cells of blastocyst and mesodermal cells, surrounds embryo and other 3 embryonic membranes, fuses with amnion as it enlarges, eventually becomes part of placenta

17
Q

Describe the yolk sac and allantois

A

Forms outer structure of umbilical cord, not as important

18
Q

Describe the placenta and it’s function

A

forms fetal and maternal tissue, fetal portion developing from chorion. Supplies nutrients and oxygen to fetus and carries away waste, produces hormones necessary for maintaining pregnancy

19
Q

What are chorionic villi

A

Finger-like projections that develop from the chorion; they grow to form part of the placenta; grow into endometrium. They become surrounded by mother’s blood in endometrium however mother and fetus blood do not mix due to layers of cells separating the two blood supplies. However, exchange of materials can occur by diffusion and active transport.

20
Q

What vessels deliver nutrients and carry away waste from the fetus.

A

2 umbilical arteries carry blood to chorionic villi to diffuse to the mother’s blood stream. Single umbilical vein carries blood from placenta through umbilical cord to fetus.

21
Q

When does the embryo take on a recognizable human form, and have all organs (although not functioning)

A

week 8 of pregnancy

22
Q

What milestone occurs at week 16-20

A

Fetus starts to move, kick and turn.

23
Q

List some changes the mother undergoes during pregnancy

A

Enlarged belly and breasts, increase size of heart and blood volume, increased urine production (due to increase blood flow),

24
Q

What is the difference between pregnancy and gestation

A

Gestation is the period of time between conception and birth. Pregnancy is the series of changes that takes place in a woman’s body and tissues as a result of the developing fetus. During a pregnancy there may be multiple gestations, in the case of twins for example.

25
Q

Describe the changes to a women’s body prior to labor

A

Hormonal changes causes the pelvis to soften, increases the uterus response to stimuli, causing more contractions,

26
Q

Summarize the first stage of labor

A

Dilation of the cervix, contractions increase and become more intense, contractions shorten the uterus which pulls on the cervix, head of fetus pushed towards cervix, birth canal complete.

27
Q

What occurs during the second stage of labor

A

water breaks, stage of expulsion, uterine contractions and abdominal muscle contractions aid movement of the baby

28
Q

What occurs during the third stage of labor

A

Baby breathes with own lungs, umbilical cord cut, veins and arteries within contract, placenta, membranes and umbilical cord expelled (afterbirth)

29
Q

Why is there usually minimal blood loss during childbirth

A

Placental blood vessels constrict, contractions from uterus shut uterine vessels, blood clots form

30
Q

What is the function of the ductus venosus

A

Allows blood in the fetus to bypass the liver as it’s function is not yet necessary; the mother’s liver serves the fetus instead.

31
Q

What is the function of the ductus arteriosus

A

Vessels allowing blood to bypass the lungs, allows blood in pulmonary artery to flow directly to aorta

32
Q

What is the function of the foramen oval

A

Allows blood to flow directly from right atrium to left atrium, this is so highly oxygenated blood from the placenta can immediately flow through aorta to developing fetal tissues

33
Q

What changes in the baby after birth

A

Ductus arteriosus, ductus venosus and foramen oval must close so blood can flow to organs that are now required to function.

34
Q

Name some changes the mother’s body undergoes due to pregnancy

A

Bodily functions slow down to allow nutrients to stay in the blood for longer and supply the fetus through diffusion by the placenta. Constipation occurs due to the stomach emptying slowly. Concentration of nutrients being higher in the blood means more is lost in the blood. Blood volume and heart rate increases to facilitate for the fetus’s nutrient needs

35
Q

Describe some dietary requirements that come with pregnancy

A

65g protein a day, 850kj more a day, folic acid increase (bread, cereal), calcium, fluoride, vitamin A

36
Q

What is listeriosis

A

An infection that occurs by eating food containing the bacteria listeria monocytogenes. This can cause miscarriages or stillbirths

37
Q

What is a teratogenic agent

A

Is an agent that causes physical defects in the fetus. Examples are anti-tumor drugs, antibiotics and marijuana

38
Q

What defects can drinking alcohol inflict on a fetus

A

Intellectual disabilities, slow growth, lower birth weight, malformed arms and legs, nervousness

39
Q

What risk does thalidomide pose

A

Limb malformation

Human Bio (6 decks)

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