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human development Flashcards

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1
Q

What is the result of the union of sperm and egg?

A

A zygote (2n).

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2
Q

How many sperm does a male produce in a lifetime?

A

About 525 billion

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3
Q

How many sperm are released during sexual intercourse, and how many typically reach the egg?

A

Hundreds of millions released; only a few thousand survive the trip to the egg.

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4
Q

How many eggs are females born with and how many are released?

A

2 million eggs at birth; ~450 eggs released during lifetime.

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5
Q

What is the main function of mitochondria in sperm?

A

To produce ATP for motility (2,500 mitochondria per sperm).

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5
Q

From which parent do embryos inherit mitochondrial DNA (mtDNA)?

A

Only from the mother (maternal inheritance).

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6
Q

Why do the largest animals tend to have the tiniest sperm?

A

Sperm size and number depend on evolutionary pressures, not body size

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7
Q

What is the purpose of the acrosome in sperm?

A

Contains enzymes (hyaluronidase & acrosin) that dissolve the egg’s zona pellucida

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8
Q

How long does sperm production take?

A

About 60–74 days.

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9
Q

What secretions are in semen and what are their functions?

A
  • Seminal vesicles: Fructose and prostaglandins.
  • Prostate: Buffers vaginal acidity.
  • Bulbourethral glands: Mucus to neutralize urethra acidity.
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10
Q

What is sperm capacitation?

A

Maturation step in female tract, destabilizing sperm head membrane to enable fertilization (~10 hours).

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10
Q

What happens during the acrosome reaction?

A

Acrosin digests zona pellucida, allowing sperm to fuse with the egg.

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11
Q

What are the two blocks to polyspermy?

A
  • Fast Block: Na⁺ influx depolarizes egg membrane.
  • Slow Block: Cortical granules create a fertilization envelope.
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12
Q

What is the morula?

A

A solid ball of 16–32 cells formed ~96 hours after fertilization.

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13
Q

What is gastrulation and when does it occur?

A

Cell migration forming 3 germ layers (~9 days post-fertilization).

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13
Q

When does implantation occur? What hormone is needed?

A

5–9 days post-fertilization; progesterone is required

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14
Q

What tissues do the ectoderm, mesoderm, and endoderm form?

A
  • Ectoderm: Skin, nervous system, retina.
  • Mesoderm: Heart, muscles, kidneys.
  • Endoderm: Lungs, liver, digestive lining.
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14
Q

What is the primitive streak?

A

A structure formed on day 15 marking the start of gastrulation and bilateral symmetry.

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15
Q

Name the four extraembryonic membranes.

A
  1. Amnion
  2. Yolk Sac
  3. Allantois
  4. Chorion
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15
Q

What does “ontogeny recapitulates phylogeny” mean?

A

Embryo development shows stages resembling evolutionary ancestors

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16
Q

What were the issues with Thalidomide?

A

Caused birth defects (teratogen); occasional defects despite animal testing resulting in no arms or legs

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17
Q

What effects does fetal alcohol syndrome (FAS) have?

A

Growth deficiencies, facial abnormalities, cognitive and coordination problems

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17
Q

What changes occur in a fetus by 8 weeks?

A

Major organs formed, limb buds develop, designated as a “fetus.”

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18
Q

When is fetal sex visible via ultrasound?

A

By the end of the first trimester (~12 weeks).

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18
What crosses the placenta between mother and fetus?
Gases, viruses (like Rubella, HIV), drugs, and IgG antibodies
18
What determines primary and secondary sex determination?
* Primary: SRY gene (testes) or DAX1 (ovaries). * Secondary: Hormones like testosterone or estrogen.
19
What physical features appear by 3–4 weeks gestation?
Eyelashes, eyebrows, hair, nails
19
What is a teratogen?
Any agent (radiation, drugs, chemicals, infections) causing developmental disturbances.
20
When is the "age of viability" for a fetus?
28 weeks (7 months)
21
What are the three stages of labor?
1. Dilation (10 cm cervix) 2. Expulsion (birth) 3. Placental delivery
21
What hormone induces uterine contractions during childbirth?
Oxytocin (also prostaglandins).
22
What triggers lactation after childbirth?
Decrease in estrogen/progesterone, and prolactin secretion.
23
What is Type II hypersensitivity (EF) related to Rh factor?
Rh- mother, Rh+ fetus causes maternal antibody attack on fetal RBCs.
24
What role does oxytocin play after birth?
Stimulates milk ejection and uterine contraction.
25
What is infertility?
Inability to conceive after one year of trying.
26
What are common causes of male infertility?
Low sperm count, poor sperm quality, smoking, hormone disruptors
27
How does in vitro fertilization (IVF) work?
Drug-induced egg production, egg retrieval, sperm fertilization in vitro, embryo implantation.
28
What ethical issues does IVF raise?
Ownership of embryos, multifetal reduction, embryo freezing, cloning concerns
29
What is the "Grandmother Hypothesis"?
Menopause may have evolved to let women invest energy into grandchildren, improving survival.
30
What are the pros and cons of embryonic stem cells?
* Pros: Totipotency, potential cures, transplant possibilities. * Cons: Ethical issues (destruction of embryos, cloning risks).
31
path of sperm in detail?
Sperm is stored in last stretch of the epididymis until needed. o Just before ejaculation, sperm passes through the vas deferens, ampulla, seminal vesicle, the ejaculatory duct & the urethra. o Seminal vesicles secrete the fructose (nourishes sperm) & prostaglandins (triggers contractions in the female tract thus aiding sperm movement). o Prostate gland secretions help to buffer the acidity (pH 3.5-4) of the vagina & urethra. Fertility & mobility is improved at pH 6. o Bulbourethral glands (Cowper’s) secrete mucus-rich fluid into the urethra during arousal. This sperm mucus neutralizes any trace of acidity in urine left in the urethra.
32
what is cleavage?
Development begins with cleavage, a series of rapid cell divisions that results in a multicellular ball. * Cleavage continues as the embryo moves down the oviduct toward the uterus.
33
what is a blastocyst?
forms about 6–7 days after fertilization & * consists of a fluid-filled hollow ball with * about 100 cells & * a small clump of inner cells
34
what is the inner cell mass?
a small clump of innercells which eventually forms the fetus
35
what is grastulation?
About 9 days after conception, the embryo * undergoes gastrulation, an organized migration of cells.
36
what are the three stages of grastula?
ectoderm, the outer layer that forms: nervous system, skin & retina 2. mesoderm, the middle layer that forms: heart, kidneys, muscles, & 3. Endoderm, the innermost layer: lungs, liver, the innermost lining of the digestive tract
37
what does the yolk sac do?
first site of red blood cell location
38
what does the allantois do?
the blood vessels become the embilical cord
39
what does the chorion do?
contributes to the placenta
40
what does the amnion do?
envelops the embryo in a protective amniotic fluid
41
overview of development order?
gamete formation, fertilization, cleavage, gastrulation, organ formation, growth and tissue formation.
42
what is DES?
originally prescribed to prevent miscarriages
43
what is the slow block?
a fertilization envelop (a physical barrier) is formed by lifting the vitelline membrane from the plasma membrane * Eggs release material (Cortical granules) into the extracellular space. * Within minutes, structure prevents fertilization
44
what is the fast block?
involves the opening of Na+ channels in the egg plasma membrane. * Na+ flows into the egg cell, depolarizing the membrane. * This depolarization prevents additional sperm from fusing to the egg plasma membrane
45
what is the process in order of cleavage?
zygote, 2 cells, 4 cells, 8 cells, morula (ball of many cells), blastocyst (hollow ball), then cross section of blastocyst
46
what happens after cleavage and in order?
gastrulation, creates a gastrula, contains ectoderm, mesoderm, and endoderm
47
what hormone is required for implantation?
progesterone
48
how is thalidomide still used?
used to treat cancer of plasma cells, TB, and shrinking of cancer cells,
49
what does prostaglandins do?
induces labor – * produced in many different tissues & may have different & opposite effects in different tissues – depending on receptor. Involved in inflammation - pain
50
three stages of child birth?
dilation, expulsion, placenta dlivery

biology (14 decks)

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