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35 Cards in this Set
- Front
- Back
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How many chromosomes are there in a human egg once it is fertilized? |
46 |
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Why must the egg be fertilized within 12-24 hours of it's release? |
After this period of time it loses it's capacity to develop. |
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Why do so few sperm arrive in the oviduct where the egg is? |
Many sperm are trapped by the cervical mucus only the best sperm are let through. |
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Why is the first sperm to reach the egg unlikely to be the sperm that enters and joins with it? |
The effort of many sperm combined is needed to break through the membrane. |
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Explain what the process of cleavage is. |
Cleavage is when the cell splits itself many times while the group of cells remains the same size. |
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How does a morula differ from a blastocyst. |
A blastocyst is filled with fluid and has two different groups of cells. |
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From which group of cells, the trophoblast or the inner cell mass, does the embryo develop? |
The inner cell mass. |
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Explain what implantation is. |
The blastocyst attaches itself to the endometrium with the inner cell mass positioned against the endometrium and the trophoblast secretes enzymes that can digest part of the endometrium so the blastocyst can sink into the uterine wall. |
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What is hCG and how long is it secreted? |
A hormone secreted by the blastocyst that has the same effect as the lutenizing hormone. It maintains the corpus luteum so the secretion of estrogen and progesterone are continued. It is secreted for four months until the placenta is able to produce estrogen and progesterone. |
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What is the amniotic cavity and where is it formed? |
The amniotic cavity is an embryo supporting structure it is formed between the inner cell mass and the trophoblast. |
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Name each of the three layers of the amnionic disk. |
ectoderm, mesoderm, endoderm. |
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Name the process that results in the formation of the primary germ layers. |
Gastrulation |
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What is morphogenesis? |
A series of events that form distinct structures of the developing organism. |
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Explain how the development of the primary germ layers is related to differentiation. |
All cells, tissues, and organs are derived from the primary germ layers through differentiation. |
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What is neurulation? |
When the notochord folds and develops into the neural tube which will eventually become the spinal chord and the brain. |
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Other than neurulation, identify two events that occur during the third week of development. |
The heart forms and begins to beat. Lungs and kidneys take shape. Limbs begin to form. |
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Identify four events that occur between the fifth and eight weeks and when do they occur? |
Fifth week the eyes open and the cells of the brain differentiate rapidly. The sixth week the limbs lengthen and the gonads start producing hormones that will influence the development of external genitalia. The seventh and eighth weeks the embryo has distinct human characteristics, organs are formed and the nervous system begins to coordinate body activities and the external genitalia are still being formed. By the end of the eighth week 90% of organs are formed. |
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At what point is the embryo termed a fetus? |
At the end of 8 weeks. |
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Name the extra-embryonic membranes |
Amnion, Yolk sac, Allantois, and Chorion |
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From which extra-embryonic membranes does the placenta and umbilical cord develop? |
The Chorion and the Allantois |
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Summarize the role of the placenta. |
Transports nutrients, waste, oxygen and antibodies. Stores nutrients. Secretes hormones and allows hormones to diffuse into the mother's blood and vis versa. |
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Summarize the role of the umbilical cord. |
The umbilical cord attaches the fetus from its navel to the placenta. |
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What are teratogens? |
Substances that can harm a fetus if it is ingested by the mother. |
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Give three examples of threats that teratogens pose to the developing baby. |
eye disorders, cleft palette, slow brain development. |
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What hormones are involved during parturition? |
Oxytocin stimulate the uterine muscles directly and through prostaglandins. |
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What is a caesarian section? |
When a physician makes an incision in the mother's abdomen and uterus and delivers the baby through the incision. |
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What is lactation? |
The secretion and formation of breast milk |
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Describe the role of oxytocin in lactation. |
Oxytocin causes contractions in the mammary lobules which contain alveoli, which are cells that produce milk. These contractions cause milk to flow to the ducts where the infant can draw it out by suckling. |
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Give two reasons a man could be infertile or sterile, and identify two reproductive technologies that could help. |
Low sperm count, high proportion on non-viable sperm. Artificial insemination, In Vitro Fertilization. |
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Give two reasons a woman could be infertile or sterile, and identify two reproductive technologies that could help.
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Failure to ovulate, blocked oviducts. Superovulation, surrogate mothers. |
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What is the most effective way to avoid conceiving a child? |
Abstinence |
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Which technology for preventing conception also protects against the transmission of sexually transmitted infections? |
A condom |
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What forms from the ectoderm?
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Epidermis (outer skin) and associated structuresNervous tissue and sense organsPituitary gland tooth enamel adrenal medulla eye lens.
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What forms from the mesoderm?
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Dermis cellular lining of blood vessels, lymphatic vessels, body cavity muscle tissue, connective tissue adrenal cortex kidneys and ureters heart spleen internal reproductive organs adrenal cortex.
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What forms from the endoderm? |
Cellular lining of respiratory tract, digestive tract, urinary bladder, urethra liver, gallbladder, tonsils, parathyroid glands, thyroid glands, thymus, pancreas |
