Exam 1: Embryology

Question 1

What is embryology

Answer 1

Biological science branch that focusses on study of the individual in the prenatal stage

Gametogenesis to birth

Question 2

Gametogenesis

Answer 2

Male:
Spermatogonia –> spermatozoa

Female:
Oogonia –> Oocytes

Both haploid cells

Question 3

Fertalization

Answer 3

Oocyte + Spermatozoon = Zygote

Question 4

Zygote

Answer 4

Primary cell embryo comes from

Question 5

Fertilization Steps (8)

Answer 5

1. Spermatozoids deposited in vagina/uterus
   •seminal secretions protect from pH (acid to alkaline)
   •stop acrosome activity until right location - uterine tube
2. Spermatozoa capacitation
   •loss of surface cholesterol and glycoproteins
   •spermatozoon and acrosome membrane fuse - acrosome reaction
3. Enzymes from acrosome released
   •hyaluronidase, cathepsins
4. Spermatozoon breaks through oocyte’s corona radiate
   •follicular cells surrounding oocyte

5.Spermatozoon penetrates zona pellucida (glycocalyx) of oocyte *still in metaphase II)
•zona pellucida alters to repel other spermatozoa

6. Spermatozoon’s membrane fuses with oocyte’s membrane
   •once membranes fuse - zona pellucida changes conformation to prevent other sperm from entering
7. Genomic material from spermatozoon is released into cytosol of oocyte
   •oocyte completes meiosis II - formation of female pronucleus
   •Spermatozoon’s nucleus rehydrates - male pronucleus
8. Fusion of pronuclei = zygote

Question 6

Outcomes of fertilization

Answer 6

Oocyte finishes meiosis - which was halted at metaphase II

Chromosome numbers re-established - pronuclei fusion

Sex is set

Growth begins via mitosis

Question 7

Sex determiation

Answer 7

Mammals:
XX - female
XY - male

Birds:
ZW - female
ZZ - male

Question 8

Growth phases

Answer 8

Growth begins with mitosis

Segmentation/cleavage

Gastrulation

Body shape acquisition:

Question 9

Growth phases - segmentation/cleavage

Answer 9

Zygote divides into blastomeres (mitosis)

Blastomeres form a sphere (n>16) = morula

Morula (16+ blastomeres) differentiates

Morula migrates to uterine body from uterine tube, keeping zona pellucida
•fluid fills cavity - blastocoel
•Once blastocoel formed - now a blastocyst

Question 10

What does morula differentiate into

Answer 10

Trophoblast - becomes the placenta

Embryoblast - becomes the embryo

Question 11

What signals the end of segmentation/cleavage

Answer 11

Blastocyst formation

Question 12

Growth phases - gastrulation

Answer 12

Embryoblasts goes from a collection of cells to 3 tissue types

Ectoderm - on outside of blastocyst
Endoderm - on inside of blastocyst
Mesoderm - in middle of blastocyst

Question 13

Gastrulation - ectoderm

Answer 13

Starts elongating

Primitive node

Primitive groove

Notochord

Question 14

Notochord

Answer 14

Forms intervertebral discs

Kinda like a rope that goes along the axis, in the middle

Kinda like an embryonic spinal cord

Question 15

What signals the end of gastrulation

Answer 15

Notochord formation

Question 16

Growth phases - body shape acquisition

Answer 16

Sketches of organs

Gene regulatory networks

Includes:
Neurulation
Mesodermal differentiation
Somatopleural tubulation

Question 17

Body shape acquisition - neurulation

Answer 17

Ectoderm

Formation of: 
Neural plate (neuroectoderm)
Neural groove
Neural tube - will form CNS
Neural crest cells (from neural tube) - will from PNS and adrenal gland

Question 18

Body shape acquisition - Mesodermal differentiation

Answer 18

Mesoderm

Paraxial mesoderm
Intermediate mesoderm
Lateral mesoderm

Question 19

Paraxial mesoderm

Answer 19

Next to axis - next to notochord

Somitomeres - cranial structures

Somites - axial skeleton
•Dorsal vertebrae, muscle, dermis

Question 20

Intermediate mesoderm

Answer 20

Mesonephros
•Urinary and reproductive organs

Mesonephros - kidney

Question 21

Lateral mesoderm

Answer 21

Divides into:

Somatopleure - attaches to ectoderm
•Thorax and abdominal structures, mesothelium, limbs

Splachnopleure - attaches to endoderm
•Epithelium and connective tissue - respiratory, digestive, thyroid, parathyroid

Question 22

Body shape acquisition - tubulation or embryo folding

Answer 22

Tubulation of Somatopleure and Splachnopleure

Cranio-caudal folding

Lateral folding

Question 23

What fluid infiltrates the morula

Answer 23

Embryotroph infiltrates morula and becomes the blastocoel

Question 24

What is embryotroph

Answer 24

Substance secreted by uterine glands that serves as nutrients of the embryo at this stage

Question 25

Embryological origin of tissues

Answer 25

Epithelium - ectoderm, mesoderm, endoderm
•Epidermis (outer layer of skin) comes from ectoderm
•Dermis (under epidermis) comes from mesoderm
•Linings of organs comes from endoderm

Musculoskeletal - mesoderm

Connective - mesoderm

Nervous - ectoderm

Question 26

Signaling

Answer 26

Gene regulatory networks (GRNs)

•Highly conserved

Question 27

Different types of signaling (5)

Answer 27

Paracrine
Direct contact
Autocrine
Synaptic
Endocrine

Question 28

Paracrine signaling

Answer 28

Cell sends signals to another cell that is in close proximity but not touching

Question 29

Direct contact signaling

Answer 29

Cells have to be touching to send signals

Gap junctions, tight junctions

Question 30

Autocrine signaling

Answer 30

Cell produces a signal that acts on itself

Question 31

Synaptic signaling

Answer 31

Sending signals through that acts on a synaptic junction

Question 32

Endocrine signaling

Answer 32

Cell produces a signal that goes into blood

Signal travels through blood to another cell, then acts on that cell

Question 33

Most important types of signaling for embryology

Answer 33

Paracrine
Direct contact
Autocrine

Question 34

Outcomes of signaling

Answer 34

Division
Differentiation
Shape change
Apoptosis