Reproduction and Developmental Biology Flashcards

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1
Q

What is gastrulation?

A

Conversion from a bilaminar to a trilaminar embryo

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2
Q

Fertilization occurs in the ___________

A

Oviduct

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3
Q

What begins the process of gastrulation?

A

Epiblast cells invaginate inwards through the primitive streak to form three cell germ layers: ectoderm, mesoderm and endoderm —> embryo is now in the gastrula stage

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4
Q

Primitive streak

A

Forms in the epiblast layer (as it thickens)
Defines left/right and top/bottom axes of the embryo
Crucial structure in the process of gastrulation

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5
Q

Invagination through primitive streak creates an opening called the ___________, which further deepens to become the _________

A

Blastopore
Archenteron (gut tube)

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6
Q

What structure eventually becomes the digestive tract

A

The archenteron (center cavity)

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7
Q

The blastopore eventually develops into:

A

The anus (deuterostomes) or the mouth (protostomes)

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8
Q

What structures are formed from the ectoderm?

A
  • CNS and PNS
  • Sensory parts of ear, eye, and nose
  • Epidermis layer of skin, nails, and hair
  • Enamel of teeth
  • Pigmentation cells
  • Adrenal medulla
  • Mammary and sweat glands
  • neural tube
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9
Q

What structures are formed from the mesoderm?

A
  • Bones
  • Muscles
  • circular/lymphatic system
  • somites
  • kidney
  • dermis of skin
  • Cardiovascular system
  • Gonads
  • Adrenal cortex
  • Spleen
  • Notochord
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10
Q

What structures are formed from the endoderm?

A
  • epithelial living of digestive, respiratory systems
  • gall bladder
  • Stomach
  • Pancreas
  • Liver (parts of it)
  • Lungs
  • Bladder lining
  • Thyroid and parathyroid
  • Thymus
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11
Q

What stage comes after the gastrula stage?

A

Neurula stage

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12
Q

Neurulation

A

Formation of the nervous system
Beginning of organogenesis

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13
Q

Organogenesis

A

Formation of new organs

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14
Q

Steps in formation of the nervous system:

A

0) “Pre-step”: formation of the notochord
1) Notochord stimulates overlying ectoderm to thicken, forming the neural plate
2) Neural plate folds onto itself, forming the neural fold/groove
3) Neural fold/groove continues to fold until edges touch, creating a hollow tube called the neural tube
4) The neural tube becomes the CNS

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15
Q

What occurs during folding of the neural tube?

A

Some cells at the crest migrate and differentiate into neural crest cells which migrate to form the PNS, teeth, pigmented cells and craniofacial bones

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16
Q

What layer do neural crest cells come from?

A

Ectoderm (not mesoderm)

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17
Q

What occurs to the mesoderm during the final stages of organogenesis?

A

Mesoderm cells called somites form two masses alongside the notochord which go on to form the vertebrae and skeletal muscles associated with the axial skeleton

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18
Q

Stem cells

A

Undifferentiated cells with potential (potency) to become many types of cells

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19
Q

Totipotent cells

A

Stem cells that can become any cell
Single cell that can produce an entire organism
Es: zygote, blastomeres of morula

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20
Q

Pluripotent

A

Stem cells that can become any of the three germ layers
Cannot form extraembryonic tissue
Ex: ICM cells, “embryonic stem cells”

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21
Q

Multipotent

A

Stem cells that can only differentiated into a few cell types of a specific tissue type
Can only give rise to more then one germ layer of cell type, but not all
Example: hematopoietic stem cells —> many blood cells

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22
Q

Extraembryonic development

A

Development of support structures outside the fetus, which include: amnion, chorion, yolk sac and allantois
Provides protection and nourishment to fetus

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23
Q

Amnion

A
  • Innermost layer, closest to developing embryo
  • Secretes **amniotic fluid*: water cushion, protecting embryo
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24
Q

Amniotes

A
  • tetrapods (4-limb aminals with backbones/spinal columns)
  • have adapted eggs that are supported by several extraembryonic membranes
  • Mammals, reptiles, birds
  • do NOT include amphibians or frogs
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25
Q

Anamniotes

A

Organisms with no amnion
Fish, amphibians
Eggs get laid in water, water serves as cushion so they dont need it

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26
Q

Chorion

A
  • Outermost layer, surrounds the embryo
  • In placental mammals: forms the fetal half of the placenta (platform for exchange of gases, nutrients, and wastes) and forms maternal tissue
  • In egg-laying mammals: membrane for gas exchange just underneath the egg shell (against the inner surface of the egg)
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27
Q

Allantois

A
  • Outpouching sac off of the archenteron that encircles the embryo, just below the chorion
  • Stores waste for disposal
  • placental mammals: transports wastes to placenta, becomes part of the umbilical cord (which transports gases, nutrients and wastes), and eventually becomes the urinary bladder in adults
  • egg-laying mammals: initially stores waste products as uric acid, later fuses with the chorion to help with gas exchange due to its rich blood supply
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28
Q

Yolk sac

A
  • Contains yolk: functions to provide nutrients to the growing embryo
  • Yolk sac is extraembryonic while the yolk is intraembryonic (part of the embryo)
  • In placental mammals: provides nutrients to growing embryo transiently until placenta is mature and is the first location of blood cell formation for the fetus
  • In egg-laying mammals: provides nutrients to growing embryo permanently
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29
Q

Viviparous

A

Gives birth to offspring that developed within mother
Most mammals

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30
Q

Oviparous

A

Produce eggs that develop and hatch once they have been expelled from the mother
Most birds, reptiles and fish

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31
Q

Ovoviviparous

A

Hybrid, produce offspring through eggs that hatch within the parent
Some snakes and amphibians

32
Q

How are dizygotic twins formed?

A

Two ovulated eggs are individually fertilized b two different sperms
This leads to different zygotes with slightly different genetic material (due to crossing over in meiosis, chromosomes in different gametes are unique)

33
Q

Frog embryos undergo what kind of cleavage?

A

Holoblastic (like humans) even though they have a lot of yolk

Holoblastic cleavage is uneven in frogs

34
Q

Animal pole

A

Very active cleavage, little yolk in this area

35
Q

Vegetal pole

A

Very slow cleavage, lots of yolk in this area

36
Q

Gray crescent

A

Only present in frog embryos- created due to the cytoplasm rotating upon sperm entry causing the mixing of animal and vegetal poles
Located across from sperm entry point

37
Q

Where does gastrulation begin in frog embryos?

A

Frog embryos do not have a primitive streak
Gastrulation begins at the dorsal lip of the blastopore which forms at the gray crescent

38
Q

Gray crescent cells are _________, which means that:

A

Totipotent
Any cells that receives a bit of the gray crescent can develop into an entire frog embryo and any cell that does not receive gray crescent cannot develop into an entire frog embryo

39
Q

Model for all egg-laying animals:

A

Chick embryo

40
Q

Characteristics of chick embryos:

A
  • Embryo has no direct connection to mother so it needs large yolk for nutrients
  • Chalaza holds the yolk in place to ends of shell so the entire embryo has equal access
  • Due to large amount of yolk, blastula is flattened into disc (blastodisc): analogous to inner cell mass in mammals; creates a elongated blastopore due to smushed blastodisc upon gastrulation at primitive streak
  • Contain a primitive streak
41
Q

Embryonic induction

A

Organizers: Cells that secrete molecules that influence what neighboring cells become
Example: dorsal lip of the blastopore - develops into the notochord which sits below the ectoderm and secrets molecules that influences the overlying ectoderm to develop into the CNS and axes

42
Q

Egg cytoplasm determinant

A

If egg cytoplasm is unevenly distributed in the embryo (creating animal and vegetal poles), an axis is created, influencing how the embryonic cells divide during cleavage

43
Q

Homeotic genes

A

Master controller: turn gene expression on and off in various parts of the organism
- Decide which part of the embryo develops into what structures: carried out through regulating the formation of the body axes and body structures in the proper location during early embryonic development

44
Q

Homeobox

A

Common DNA sequence (the same short sequence of ~180 nucleotides) homologous across organisms that contain homeotic genes (derived from common ancestors)

45
Q

HOX (homeotic) genes

A
  • A subset of homeotic genes that are responsible for anterior-posterior (head-to-tail) position of body parts during development
46
Q

Apoptosis

A

Programmed cell death for normals development of fetus and adults
Example: fetus- removing webbing between fingers; adults- preventing cancer

47
Q

What are the main functions of the trophoblast?

A

1) Help in the formation of some extraembryonic membranes (placenta and chorion)
2) Implant the embryo into the uterus
3) Produce HCG to maintain the corpus luteum and endometrium

48
Q

Cells from the inner cell mass are considered to be which cell type?

A

Pluripotent cells: cells from inner cell mass develop into embryonic stem cells

49
Q

The blastodisc in chick embryos is analogous to which structure in mammalian cells?

A

Inner cell mass

50
Q

How are oogonia replicated and where are they replicated?

A

Mitosis division in the ovaries

51
Q

A section of a spinal cord is experimentally implanted into an embryo. No matter where it is inserted, a vertebral column grows around it. What can be concluded from this experiment?

A

The vertebral column can be induced from the spinal cord

This is a reasonable conclusion that can be made directly from the experiment

52
Q

Somites

A

Mesodermal cells that form two masses on each side of the notochord

53
Q

Blastomeres

A

Each small cell resulting from cleavage

blstomere of morula are Totipotent cells (morula = ball of blastomeres)

54
Q

What is zona hatching?

A

When the blastocyst removes its zona pellucida and replaces it with trophoblast cells in order for implantation to occur in the uterine wall

55
Q

General steps of block polyspermy:

A

Sperm penetrates egg, sodium ion diffuse into the egg causing membrane depolarization, preventing additional sperm from binding
Lasts a few seconds

56
Q

Cleavage

A

The first step of growth after the formation of the zygote
Rapid cel division without changing the total mass of the cell
Results in smaller cells called blastomeres

57
Q

Anamniotes

A

Animals that do not have an amnion
Ex: amphibians and fish (surround water serves as a cushion)

58
Q

Spiral cleavage

A

Misaligned cells that deviate away from the vertical axis (protostomes)

59
Q

Invagination along the primitive streak forms a ________, which initiates gastrulation

A

Blastopore

60
Q

what begins the process of fertilization?

A

when a sperm penetrates the plasma membrane of the secondary oocyte, both of which are haploid, forming a diploid zygote

61
Q

zona pellucida

A

glycoprotein membrane that surrounds the plasma membrane of an oocyte and ensures the same species fertilization, expresses specific receptor proteins that bind proteins expressed in the head of the sperm

62
Q

which ion triggers the cortical reaction in the egg?

A

stimulated by the release of intracellular calcium ions

63
Q

what is the purpose of the acrosomal reaction?

A

recognition process between sperm and egg before fusion –> ensures same-species fertilization

64
Q

fast block polyspermy

A

occurs when the oocyte membrane depolarizes due to sodium ions diffusion into the egg, preventing more sperm from penetrating the egg –> ensures that only one sperm penetrates the zona pellicuda and fuses with the oocyte membrane

65
Q

cortical reaction

A

also referred to as slow block polyspermy, is the exocytosis of enzymes produced by cortical granules in egg cytoplasm during fertilization

66
Q

what is the slow block polyspermy stimulated by?

A

stimulated by the release of intracellular calcium ions

67
Q

eggs (ova) are produced in the ________

A

ovaries

68
Q

oviduct

A
  • fallopian tube or uterine tube
  • allows for eggs to move form the ovary to the uterus
  • where fertilization occurs
  • not connected to ovary –> egg is swept into ovidct via fimbreiae
69
Q

uterus

A
  • muscular chamber
  • development of embryo occurs until birth
  • a fertilized ovum implants on the inside of the uterine wall (endometrium) on day 6 of fertilization
70
Q

testis

A
  • consist of seminiferous tubules for production of sperm and interstitial cells (Leydig cells) that produce male sex hormomes: testosterone and androgens at the beginning of puberty (these hormones are secreted in the presence of LH
71
Q

steroli cells

A
  • stimulated by FSH
  • serve to surround and nurter sperm
  • secrete peptide hormone: inhibin which acts on the anterior pituitary to inhibit FSH
72
Q

scrotum

A
  • where the testis are located
  • provides external cavity
  • 2°C lower than the body temperature for sperm production
73
Q

epididymis

A
  • coiled tube attached to each testis
  • serves as the site for final sperm maturation and storage of sperm
74
Q

vas deferens

A
  • transfer sperm from one epididymis to the urthera
75
Q

seminal vesicles

A
  • two glands that function during enjaculation to:
  • secretes fructose: produce ATP for energy for sperm
  • secrete viscous mucus: lubricates and cleans the urethra
  • secretes prostaglandins: stimulates uterine contractions that help sperm move into uterus