Embryogensis and Development

Question 1

Ampulla

Answer 1

Widest region of fallopian tube where fertalization usually occurs

Question 2

What are the wo major components of the ovum (outside of cellular membrane)?

Answer 2

1. Zona Pellucida: acellular mixture of glycoproteins
   
   1. Aid in protection of ovum
   2. Aid in sperm binding
2. Corona Radiata
   
   1. layer of cells that adhere to oocyte during ovulation

Question 3

Explain process and major components of Fertilization.

Answer 3

1. Sperm comes into contact with ovum (often in ampulla)
2. Sperm Penetrates ovum with acrosomal enzymes
3. Forms Acrosomal Apparatus with ovum membrane
   
   1. Tube-like structure that penetrates membrane (fusing with ovum membrane) so that pronucleus can be release into ovum for completion of meiosis II
4. Cortical Reaction Occurs after penetration
5. Fertlization Membrane is Produced
   
   1. Depolarized and impenetratable

Question 4

Two main purposes of Cortical Reaction

Answer 4

Releases of calcium ions:

1. Depolarizes the ovum membrane to prevent further fertilzation by additional sperm
2. Increase metabolic rate of the newly formed zygote

Question 5

Fertilization of two different eggs release during the same ovulatory cycle and fertilized by two different sperm. Each develop their own, chorion, amnion, and placenta.

Answer 5

Dizygotic (Fraternal) Twins

Question 6

Single Zygote splits into two. Have same genetic material. Can share embryonic structures such as placenta, chorion, and amnion.

Answer 6

Monozygotic (Identical) twins

Question 7

Three classifications of monozygotic twins.

Answer 7

1. monochorionic/monoamniotic
2. monochorionic/diamniotic
3. Diamniotic/monochorionic

Question 8

Four Major Processes that Occur after fertilization.

Answer 8

1. Cleavage
2. Blastulation
3. Gastrulation
4. Neurulation

Question 9

Brief Summary of four processes that occur after fertilzation.

Answer 9

1. Cleavage: Rapid mitotic division of the embryo forming a morula (with the first nulifying the unicellular defining character of a zygote)
2. Blastulation: Blastula with Blastocoel is formed and comprised of inner cell mass and surrounding trophoblast. (known as a blastocyst in mammals). Implantation also occurs during blastulation.
3. Gastrulation: Generation of three distinct cell layers forming a gastrula (with ectoderm, mesoderm, and endoderm)
4. Neurulation: Development of the nervous sytem.

Question 10

Important aspects of Cleavage

Answer 10

Purpose: Rapid Mitotic Division of New Embryo

1. Cells Increase two ratios
   
   1. N:C
   2. SA:V
2. Indetermine Cleavage vs. Determinite Cleavage

Question 11

Process in which cells are capable of becoming any part of the body during cleavage.

Answer 11

Indeterminate Cleavage

Question 12

Process by which cells are committed to differentiating into a specific cell during cleavage.

Answer 12

Determinate Cleavage

Question 13

Solid mass of cells created by embryonic cleavage.

Answer 13

Morula

Question 14

Important Aspects of Blastulation

Answer 14

1. Blastula (hollow ball of cells) with Blastocoel (fluid -filled inner cavity)
2. Two different cells types: Inner Cell Mass + Trophoblast

Question 15

Part of the Blastula that becomes the placental structures.

Answer 15

Trophoblasts

After Implanation into the Endometrium, the trophoblasts begin development of the:

1. Chorion: extraembryonic membrane that becomes placenta
2. Chorionic Villi: finger-like projections (that also develop into placenta)
   
   1. Penetrate into endometrium and support maternal-fetal gas exhange

Question 16

Consists and 2 arteries and 1 vein encased in a gelatinous substance and function as maternal-fetal blood exchange. Also connects placenta to developing embryo.

Answer 16

Placenta (Formed from yolk sac and allantois)

1. Arteries: deoxygynated fetal blood and waste from embryo to placenta
2. Vein: oxygynated blood from placenta to embryo

Question 17

Site of early blood cell development (functions in place of placenta until it becomes fully functional)

Answer 17

Yolk Sac

Question 18

Site of early fluid exchange between yolk sac and embryo

Answer 18

Allantois (together with yolk sac become the placenta)

Question 19

Thin tough membrane filled with amniotic fluid that surrounds the allantois. “Shock absorber” during pregnancy.

Answer 19

Amnion

Question 20

Be able to understand and analyze the major aspects of fetal develoment within this picture.

Answer 20

Question 21

Important aspects of gastrulation.

Answer 21

1. Formation of the Gastrula = Archenteron + Blastospore
   
   1. Archenteron: membrane invagination into blastocoel (gut)
   2. Blastospore: Opening of Archenteron (anus(in deuterosomes))
2. Formation of Primary Germ Layers = Beginning of Differentiation
   
   1. Ectoderm
   2. Mesoderm
   3. Endoderm

Question 22

“Atractoderm”

Answer 22

Ectoderm (what can make a person attractive)

-Skin, hair, nails, facial structures, and nervous systems

Question 23

Oderm: Means to “get around”

Answer 23

Mesoderm

• Bones and muscles
• Circulatory System

Question 24

“In-doderm” (Lining of Organs)

Answer 24

Endoderm

• Respiratory and Digestive Tract and accessory organs

Question 25

Explain Process of Neurulation

Answer 25

1. Rod of mesoderm cells form a **notochord** along axis of organism 2. Notochord induces ectodermal cells to pinch inward to form **neural fold** 3. **Neurol groove** forms as a result of the the ectoderm pinching inwards and eventually separating from surrounding neural fold to form **neural tube** 4. Neural Tube, which becomes CNS, is surrounding by **neural crest,** which become PNS 5. Ectoderm migrates over tube and crests to cover nervous system

Question 26

Interfere with embryonic development and can cause defects or death.

Answer 26

Teratogens

Question 27

Two subsequent mechanisms that result in cell specialization

Answer 27

1. Determination 2. Differentiation

Question 28

Determination

Answer 28

Commitment of a Cell lineage, which is accomplished by: 1. Uneven segregation of cellular material during mitosis OR 2. Morphogens: promote development down to a specific cell lineage

Question 29

Changes a cell undergoes due to selective transcription to take on characteristics of a specific cell lineage.

Answer 29

Differentiation

Question 30

Undifferentiated cells that give rise to other cells that will differentiate

Answer 30

stem cells

Question 31

List and describe 3 different types of stem cells

Answer 31

1. Totipotent (most potent): can differentiate into any cell (including placental structures or actual fetus) 2. Pluripotent (gastrulation): can differientiate into all three germ layers and their derivatives, but not placental strucutures. 3. Multipotent (least potent - most specialized): Can differientiate into multiple types of cells within a specific group

Question 32

Determines how many different cell types a stem cell can become.

Answer 32

Potency

Question 33

What are the roles of the inducer and responder in cell-to-cell communication?

Answer 33

Inducers promote differentiation by secreting a signal to induce another cell, which is the responder. Responder must be "competent," or able to respond to inducing signal.

Question 34

List the four types of cell to cell communcation.

Answer 34

1) Autocrine 2) Paracrine 3) Juxtacrine 4) Endocrine (Also remember that signals often occur via gradients)

Question 35

Type of cell-to-cell communication where signal that acts on the same cell the released the signal.

Answer 35

Autcrine

Question 36

Type of cell-to-cell communication where signal on cells in local area.

Answer 36

Paracrine

Question 37

Type of cell-to-cell communication where signal acts through direct stimulation of nearby cells.

Answer 37

Juxtocrine

Question 38

Type of cell-to-cell communication where signal acts on distant tissues after traveling through bloodstream.

Answer 38

Endocrine

Question 39

These are inducers made of proteins that promote differentiation and mitosis in certain tissues.

Answer 39

Growth factors (most of which only target/code for specific cells or tissue)

Question 40

Reciprocal Induction

Answer 40

When two tissues induce further differentiation on the other (i.e. one induces a signal to an adjacent cell, which in return induces a signal on the initial cell).

Question 41

Describe the Process of Apoptosis.

Answer 41

1. Cell divides into many self-containing apoptotic blebs 2. Blebs are ingested by other cells (This method prevents waste/toxins from being released into extracellular environment because pieces are still within cellular membrane; Apoptosis can be important for sculting certain anatomical features, such as the webbing between digits.)

Question 42

Process of cell death in which cell dies due to injury.

Answer 42

Necrosis (Can be harmful to other cells due to release of toxic substances)

Question 43

Regerative Capacity

Answer 43

Ability for Organism to regrow certain body partss.

Question 44

Where gas, nutrient, and waste exchange occur in an embryo.

Answer 44

Placenta

Question 45

Method by which nutrients and waste products are transfered from fetus to mother.

Answer 45

Diffusion (which requires a gradient)

Question 46

Explain how oxygen, carbon dioxide, and waste are exchanged between fetus and mother.

Answer 46

Diffusion via a gradient * Oxygen * Mother has a higher partial pressure of oxygen than child * Fetus has HbF, which has a higher affinity for O2 than maternal Hb * HbF assists with transfer and retention of oxygen in fetal circulatory system * CO2 and waste * Mother has a higher affinity for transfer and retention of CO2 and waste products (opposite of HbF)

Question 47

List the three major functions of the Placenta

Answer 47

1. Waste, gas, and nutrient exchange 2. Immune Protection (protects against pathogens and transfers antibodies to fetus) 3. Endocrine Functions (secretes est. and prog. to allow pregnancy to continue)

Question 48

List two organs that do not serve a purpose prior to birth.

Answer 48

1) Liver (detoxification and metabolism are primarily controlled by mother's liver) 2) Lungs

Question 49

List 3 shunts that block off blood flow to lungs and liver.

Answer 49

1. Foramen Ovale 2. Ductus Arteriosis 3. Ductus Venous

Question 50

Connects the right atrium to the left atrium, bypassing the lungs during fetal development.

Answer 50

Foramen Ovale (Remember than during fetal development, pressure on the right side of the heart is greater than pressure in the left side of the heart, which reverses upon birth)

Question 51

Connects the pulmonary artery to aorta, bypassing the lungs during fetal development.

Answer 51

Ductus arteriosis

Question 52

Connects the umbilical vein to inferior vena cava, bypassing the liver during fetal development.

Answer 52

Ductus Venous

Question 53

Major Milestones during First Trimester of Pregnancy.

Answer 53

Organogenesis

Question 54

Major Milestones during Second Trimester of Pregnancy.

Answer 54

1. Rapid Growth 2. Face Becomes Distinct 3. Digits Elongate

Question 55

Major Milestones during First Third of Pregnancy.

Answer 55

1. Rapid Growth 2. Brain Development 3. Transfer of Materna Antibodies to fetus

Question 56

Parturition

Answer 56

Vaginal Birth

Question 57

List events that occur during vaginal birth.

Answer 57

1. Cervix thins out 2. Amniotic Sac Ruptures 3. Uterine Smooth Muscles Contract (coordinated by **prostaglandins** and peptide hormone **oxytocin**) 4. Fetal Birth 5. Afterbirth (placenta and umbilical cord)