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Biology > Chapter 3 - Embryogenesis > Flashcards

Chapter 3 - Embryogenesis Flashcards

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1
Q

When can the acrosomal apparatus of the sperm enter the oocyte?

A

After meiosis II has come to completion.

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2
Q

What is the cortical reaction?

A

Occurs after penetration of the sperm through the membrane (through the coronal radiata and the zone pellucida).

It releases calcium ions to depolarize the membrane:

  1. To prevent fertilization by more than one sperm
  2. To increase metabolic rate of newly formed diploid zygote.

(The result is he FERTILIZATION MEMBRANE)

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3
Q

What is cleavage?

A

When the zygote undergoes rapid mitotic cell divisions.

  • the first: creates the embryo (no longer a zygote since it is multicellular now)
  • continues to multiply without growing in size: increases surface area for exchange of gas and nutrients.
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4
Q

Indeterminate versus determinate cleavage:

A

Indeterminate cleavage: the cells can still develop into complete organisms.

Determinate: committed to differentiating into a certain type of cell

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5
Q

What is a morula?

*hint: mulberry

A

After many cell divisions of “cleavage”, the embryo is a MORULA.

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6
Q

What is the ampulla?

A

The widest part of the Fallopian tube, where fertilization of the secondary oocyte generally occurs.

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7
Q

What is blastulation?

A

Process through which the morula becomes the BASTULA, which is a hollow ball of cells with a fluid-filled inner cavity (called the blastocoel)

Is mammalian blastula is called a BLASTOCYST

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8
Q

What is a blastocyst?

A

A mammalian blastula.

A hollow ball of cells with a fluid-filled interior.

Blastocoel - fluid interior
Trophoblast - surround cells. Give rise to the chorion (eventually the placenta)
Inner cell mass - protrudes inwards and gives rise to the organism itself.

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9
Q

What is the chorion?

A

Extraembryonic membrane that develops into the placenta.

The trophoblast a form chorionic villi, which penetrate the endometrium.

Chorionic villi then develop into the placenta and support maternal-feats gas exchange.

***the chorion also forms a membrane around the amnion, adding protection.

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10
Q

The umbilical cord:

What is it made up of?
What does it do?

A

Made of 2 Arteries and 1 Vein (work the reverse: the vein carries oxygenated blood) encased in a gelatinous substance.

These carry blood/waste to and from the placenta for exchange.

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11
Q

What is the yolk sac?

A

The site of early blood cell development.

Supports the embryo until the placenta is functional

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12
Q

What is the allantois?

A

Extraembryonic membrane

Involved in early fluid exchange between embryo and yolk sac.

(The allantois + yolk sac will eventually form the umbilical cord)

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13
Q

What is the Amnion?

A

Extraembryonic membrane

Surrounds the allantois and embryo. Filled with amniotic fluid. This fluid serves as “shock absorber” during pregnancy.

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14
Q

What is gastrulation?

A

The generation of three distinct cell layers (primary germ layers):

Ectoderm
Mesoderm
Endoderm

The result of gastrulation is called a Gastrula.

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15
Q

What is the archenteron?

What is the blastopore?

A

The invagination of the membrane into the blastocoel (the inside “hollow” fluid-filled portion)

*this develops into the gut

The blastopore is the opening of the archenteron.

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16
Q

What anatomical feature does the blastopore become?

A 
In deuterostomes (humans) = the anus
In protostomes = the mouth
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17
Q

What does the ECTODERM give rise to?

A

Nervous system (and adrenal medulla)

Epidermis / integument

Lens of the eye, tooth enamel

Inner ear

Lining of the mouth, anus, sweat glands, hair and nails

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18
Q

What does the MESODERM give rise to?

A

Musculoskeletal system
Circulatory system
Most of the excretory system

Gonads

Muscular and CT layers of digestive system, respiratory system, and adrenal cortex

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19
Q

What does the ENDODERM give rise to?

A

Epithelial lining of digestive and respiratory systems (incl lungs)

Organs such as the pancreas, thyroid, bladder, parts of the liver and distal urinary tracts.

20
Q

What is selective transcription (of the genome)?

A

The process by which only genes needed for a particular cell type are transcribed.

Ie only genes to produce certain hormones are turned on in certain hormone-producing cells.

Results in different cell types with highly specialized function, despite all having the same genes and coming from the same exact cell.

21
Q

What is induction?

A

The ability for one group of cells to determine the fate of other nearby cells.

Involves chemicals called INDUCERS, which diffuse from the organizing cells to the responsive cells. It ensures proximity of cells that work together within an organ.

22
Q

Neurulation

What is the process?

A

The development of the nervous system

  1. Mesodermal cells form the NOTOCHORD
  2. Overlying ectodermal cells form NEURAL FOLDS which surround a neural groove
  3. Neural folds grow toward each other until they fuse to make the NEURAL TUBE (gives rise to central nervous system)
  4. Neural crest cells at the tip if each neural fold give rise to the peripheral nervous system
23
Q

What are the stages of early development?

5

A

FERTILIZATION

CLEAVAGE

BLASTULATION
- implantation

GASTRULATION
(Happens at about 3 weeks)

NEURULATION

24
Q

What is spina bifida?

A

Failure of the neural tube to close.

Some of the spinal cord becomes exposure to the outside world (to varying degrees)

Folic acid can prevent this complication

25
Q

What is anencephaly?

A

Failure of the neural tube to close.

Some of the brain fails to develop and the skull is left open - this is UNIVERSALLY FATAL.

Folic acid can prevent this complication.

26
Q

What is a teratogen?

What are some examples?

A

A teratogen is a substance that interferes with development.

Vary based on route of exposure, length of exposure, rate of transmission, identity of the teratogen.

Examples include alcohol, prescription drugs, viruses, bacteria, environmental chemicals (such as polycyclic aromatic hydrocarbons).

27
Q

What is potency of stem cells?

What are the 3 levels of potency?

A

It’s ability to differentiate into any type of cell.

TOTIPOTENT: can differentiate into any cell type (most potent) - cells of the embryo, up until it differentiates into the 3 germ layers.

PLURIPOTENT: can differentiate into any cell type EXCEPT those in placental structures.

MULTIPOTENT: can differentiate into multiple types of cells within a particular group.

28
Q

How can cell-cell communication occur?

(Ie what are types of inducers)

(4 types)

A

AUTOCRINE: act on the same cell that produced the signal

PARACRINE: act on cells in the local area

JUXTACRINE: not via diffusion, but by directly stimulating receptors on an adjacent cell

ENDICRINE: involves secreted hormones via the bloodstream, reaches distant target tissues.

29
Q

What are growth factors?

A

Inducers; peptides that promote differentiation and mitosis in certain tissues.

30
Q

Complete vs incomplete regeneration

A

Complete regeneration: the tissue or organ lost is replaced by identical tissue.

Incomplete regeneration: the newly formed tissue is not identical in stricture or function to the tissue that was injured/lost.

HUMANS: incomplete regenerative potential.

Liver very high
Heart very low
Kidney moderate

31
Q

Telomere

Role in senescence

A

Telomeres are the ends of chromosomes. They shorten during each round of DNA synthesis, eventually become too short and the cell is no longer able to replicate.

32
Q

What is telomerase?

A

An enzyme

Expressed by germ cells, fetal cells, and tumor cells.

A reverse transcriptase that is able to synthesize the ends of chromosomes, preventing senescence.

(May play a role in the survival of cancer cells)

33
Q

Fetal circulation via diffusion (at the placental barrier)

A

Preferred method for waste, glucose, amino acids and inorganic salts.

Diffusion requires a gradient - partial pressure of O2 is HIGHER in maternal blood than in fetal blood.

Additionally, Fetal hemoglobin (HbF) exhibits a GREATER affinity for O2 than maternal hemoglobin (HbA)

34
Q

How does the immune protection of the fetus happen?

A

Crossing of antibodies across the placental membrane serves as a protective function.

35
Q

How does the placenta act like an endocrine organ?

A

It produces hormones:

Progesterone
Estrogen
Human chorionic gonadotropin (hCG)

These maintain pregnancy.

36
Q

ARTERY versus VEIN, correct biological definitions

A

ARTERY caries blood away from the heart.

VEIN carries blood toward the heart

37
Q

Why is the oxygen concentration reversed in umbilical arteries and veins?

A

Because oxygenation happens at the PLACENTA not at the LUNGS

38
Q

What is the purpose of the 3 fetal shunts ?

What are the 3 fetal shunts?

A

They direct blood away from organs that aren’t being used yet (mainly the lungs and the liver) - ways for blood to bypass these

FORAMEN OVALE

DUCTUS ARTERIOSUS

DUCTUS VENOSUS

39
Q

What is the foramen ovale?

A

One of the three fetal shunts.

Connects R atrium to L atrium. (Bypasses R ventricle - goes to L atrium and then through the aorta into the systemic circulation) this is also due to the pressure difference in the fetus: R side of heart has higher pressure than L. At birth the pressure reverses, closing the foramen ovale.

40
Q

What is the ductus arteriosus?

A

One of the three fetal shunts.

Shunts leftover blood from the pulmonary artery to the aorta. The pressure diff between R and L sides if the heart push blood through this opening.

41
Q

What is the ductus venosus?

A

One of the three fetal shunts (bypasses the liver)

Shunts blood returning from the placenta (via the umbilical vein) directly to the inferior vena cava. The liver still does receive some blood from smaller hepatic arteries.

42
Q

What happens during the 1st trimester? (By week)

A

22 days: heart starts beating, followed by development of eyes, gonads, limbs, and liver.

Week 5 - 10mm long
Week 6 - 15mm long! (Double)
Week 7 - cartilaginous skeleton hardens into bone
Week 8 - most organs formed, brain fairly developed –> known as “fetus”

At end of 3rd month, about 9cm long

43
Q

What happens during the 2nd trimester?

A
  • lots of growth
  • starts moving in the amniotic fluid
  • face takes on human appearance
  • fingers and toes elongate
  • at the end of 6 months, about 30-36cm long
44
Q

What happens during the 3rd trimester?

A
  • Months 7 and 8: continued rapid growth and brain development
  • Month 9: active transport of antibodies to the fetus; growth slows, less room for fetus to move.
45
Q

Key points of birth:

Some facts + 3 basic phases

A
  • uterine smooth muscle contractions (coordinated by prostaglandins and oxytocin)

3 basic phases:

  1. Cervix thins out + amniotic sac ruptures = “water breaking”
  2. Strong uterine contractions = “birth”
  3. Placenta and umbilical cord are expelled = “afterbirth”

Biology (11 decks)

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