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Embrology > Exam 2 embryology > Flashcards

Exam 2 embryology Flashcards

1
Q

Sperm

A

develops from a classical cell.

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2
Q

Head

A

known as the “acrosome” and is derived from the golgi apparatus. Contains a vesicle of digestive enzymes to penetrate into the egg and a nucleus of DNA.

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3
Q

Midpiece

A

aggregates of mitochondria for ATP production for motility

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4
Q

Flagella

A

referred to as the “axoneme”. 9 + 2 arrangement of microtubules containing “dynein”, an ATPase enzyme to hydrolyze ATP for energy and movement of the ATPase enzyme to hydrolyze ATP for energy and movement of the flagella.

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5
Q

Capacitation

A

the maturation process of sperm which occurs in the reproductive tract and is is achieved under the control of chemical signals from the egg.

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6
Q

Kartageners Syndrome

A

ack of Dynein enzyme therefore results in decreased motility of sperm and infertility. In extreme cases there is an absence of flagella and cilia leading to respiratory infections.

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7
Q

Situs Inversus

A

some individuals with Kartageners will also present with “Situs Inversus” which is a mirror image layout of anatomical structures.

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8
Q

Polyspermic Fertilization

A

more than one sperm penetrating into the egg cytoplasm resulting in an excess of genetic material and a lethal result to the embryo. (Polyspermia)

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9
Q

Egg

A

accumulates cytoplasm during oogenesis or formation where the sperm loses volume during its development.

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10
Q

Cytoplasm

A

contains proteins, ribosomes, mRNA, tRNA, paracrine factors and transcription factors and enzymes for repair processes of minor DNA defects.

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11
Q

Egg Cell Membrane

A

fusing site for sperm

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12
Q

Extracellular envelope

A

sperm/egg recognition sites and for species specific recognition.
Vitelline Envelope in invertebrates and Zona Pellucida in vertebrates.

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13
Q

Cumulus

A

ovarian follicular cells outside the zona pellucida.

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14
Q

Corona radiata

A

innermost layer of cumulus cells.

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15
Q

Cortex

A

inside the cell membrane. Contains “actin microfilaments” to aid in sperm entry.

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16
Q

Cortical granules

A

proteolytic enzymes used to prevent polyspermia

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17
Q

Fertilization occurs in the upper third of the fallopian tube near the “Ampulla” region.
Fertilization is considered - Carnegie Stage 1: 1 day

A
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18
Q

Translocation

A

movement of sperm through the regions of the reproductive tract aided by smooth muscle contraction in the “myometrium” of the uterine wall.
Maturation and motility of sperm increases in the fallopian tube

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19
Q

Thermotaxis

A

increasingly warmer temperatures up the fallopian tube create hyperactive motility.

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20
Q

Chemotaxis

A

chemical signals from the cumulus region aid in translocation.

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21
Q

Zona pellucida proteins (ZP 3)

A

bind the acrosomal region of sperm and initiate G-protein linked
second messenger system to open “calcium” channels. Calcium influx releases enzymes from the acrosomal region for digesting and entry through the zona and egg cell membrane. This event
stimulates the cortical granules to release all other sperm cells bound to ZP 3 proteins preventing
polyspermia. Anti-sperm antibodies may inhibit the binding of the sperm to the zona layer therefore
potentially leading to infertilization.

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21
Q

Zona pellucida proteins (ZP 3)

A

bind the acrosomal region of sperm and initiate G-protein linked
second messenger system to open “calcium” channels. Calcium influx releases enzymes from the acrosomal region for digesting and entry through the zona and egg cell membrane. This event stimulates the cortical granules to release all other sperm cells bound to ZP 3 proteins preventing polyspermia. Anti-sperm antibodies may inhibit the binding of the sperm to the zona layer therefore potentially leading to infertilization.

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22
Q

Gamete Fusion

A

Side of the sperm head fuses with the egg membrane (mammals). Microvilli (actin myofilaments) binding regions facilitate the recognition and binding process.

23
Q

Importance of the Zona pellucida (ZP) encircling the developing embryo while in the fallopian tube.
Early release of the embryo from the ZP in the fallopian tube may allow attachment of the embryo
to the wall of the tube and “ectopic” pregnancies.” Once out of the tube and in the uterine space, a
failure of the embryo to release from the ZP can prevent the embryo from adhering to the uterine
wall and a loss of the pregnancy (miscarriage or spontaneous abortion)

A
24
Q

Joining of Genetic Material

A

The egg nucleus has been arrested in metaphase of meiosis II and resumes the meiosis process upon entry of the sperm into the egg cytoplasm and calcium influx. The egg nucleus is now “haploid” following the completion of meiosis. Microtubule formation draws the pronucleus of the sperm and the pronucleus of the egg towards each other.

25
Q

Zygote

A

the “fertilized egg.” The zygote is not considered a “diploid” embryo until after the the first mitotic division or cleavage takes place.

26
Q

Cleavage

A

division of the blastomeres (cytokinesis) beginning approximately 18-24 hours after fertilization in the fallopian tube.

27
Q

Rotational Cleavage

A

division in two planes, meridian and equatorial. Blastomeres do not divide in synchrony resulting in odd numbers of cells.

28
Q

Genetic Control from the diploid nucleus of the zygote is driving or controlling the cleavage process.
Abnormalities in the genome usually results in cessation of mitosis and development of the embryo therefore the termination of pregnancy.

A
29
Q

Compaction

A

a tight bonding of the blastomeres through adhesion proteins, “cadherins”, to form a compact ball of cells. “Tight junctions” stabilize the outer ring of cells while communication is established through “gap junctions”.

30
Q

Morula

A

solid ball of blastomeres forming at approximately 3 days post fertilization in humans.

31
Q

It is at about the stage between the Morula and Blastocyst that the human embryo is exiting the oviduct and entering the uterine space.

A
32
Q

Cavitation

A

“Sodium” influx into the center of the morula creates a hypertonic environment drawing water in to the central part of the cell and resulting in a blastocoel and the “Blastocyst” stage by approximately day 5 in humans.

33
Q

Trophoblast (trophectoderm)

A

outer ring of cells which do not produce embryonic structures but lead to formation of the outer-embryonic membranes. Trophoblast cells adhere to polysaccharide chains attached to the endometrial lining of the uterine wall. The polysaccharides are synthesized by “estrogen & progesterone” hormones released from the corpus luteum.

34
Q

Inner Cell Mass (ICM)

A

“Embryonic Stem Cells” which give rise to the embryonic structures.

35
Q

Zona pellucida encircles the developing embryo while in the fallopian tube. Early release may allow attachment to the wall of the tube and “ectopic” pregnancies. A failure of the embryo to release from the zona pellucida can prevent the embryo from adhering to the uterine wall.

A
36
Q

Hatching

A

expanding Blastocyst and enzymes from the trophoblast breakdown the zona pellucida to expose the embryo.

37
Q

Contact between the trophoblast and the endometrium releases enzymes for burrowing and
“Implantation” within the uterine wall.

A
38
Q

Gastrulation

A

organized cell movements within the embryo to produce three distinct germ layers known as the “Gastrula” stage of the embryo.

39
Q

Neural Plate

A

columnar shaped cells in the dorsal ectoderm

40
Q

Neurulation

A

process of the neural plate forming the neural tube

41
Q

Primary Neurulation

A

neural plate cells invaginate, proliferate, and pinch off to divide the “ectoderm” into;

42
Q

1) Neural tube which will form the brain and spinal cord. The neural tube eventually separates from the ectoderm.
2) Epidermis of skin
3) Neural crest cells which forms the peripheral nervous system

A
43
Q

Medial Hinge Points (MHP’S)

A

anchored to the notochord underneath and allow for bending of the neural plate. Failure of the tube to close leads to neural tube defects such as “spina bifida”.

44
Q

Folate

A

as a dietary supplement during pregnancy has proven crucial for complete closure of the neural tube

45
Q

Secondary Neurulation

A

Messenchymal cells aggregate to from a solid neural rod that hollows out to form the neural tube.

46
Q

Humans, frogs, birds

A

Most formation of neural tube is through primary neurulation with only the most caudal region of the tube forming through secondary neurulation.

47
Q

The Nervous System is the first system to begin forming in the embryo by the events above. Note, it is not the first to complete developing but only the first to begin formation. (The heart, mentioned below is the first organ and system to complete the development.)

A
48
Q
  • Epidermis & Integumentary Structures
A

Further specification of the ectoderm leads to these structures.

49
Q

Skin

A

largest “organ” in the body

50
Q

Epidermis

A

is derived from the embryonic ectoderm following Neurulation.

51
Q

Glands

A

invagination or folding in of the epidermis and dermal cells

52
Q

Keratinocytes

A

cells in the epidermis which produce “keratin”, a waxy/waterproofing barrier across the outer, superficial surface of the skin.

53
Q

Melanocytes

A

cells of the epidermis that secrete “melanin”, sometimes known as the body’s natural sun screen. Provides darker pigmentation to the skin to protect underlying cells/tissues from harmful UV irradiation

54
Q

Lanugo

A

a very fine, soft, usually unpigmented, downy hair. It is the first hair to be produced by the fetal hair follicles, and it usually appears at about five months of gestation. It is replaced by hair which is called vellus hair.

Embrology (3 decks)

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