Intro to embryology

Question 1

What is Embryology?

Answer 1

The study of the continuous process of the development of the human from a single cell to a baby

Question 2

What is developmental anatomy?

Answer 2

The structural change of a person from fertilization to adulthood

Question 3

What is Teratology?

Answer 3

The division of embryology and pathology that deals with abnormal development (birth defects)

Question 4

What are 3 stages of prenatal development?

Answer 4

1. Preimplantation period
2. Embryonic period (1-8 weeks)
3. Fetal period (9th week)

Question 5

What is a Trimester?

Answer 5

A period of 3 months, one third of the length of a pregnancy

*Most critical is the 1st trimester (13 weeks)

Question 6

What is Preimplantation period?

Answer 6

1. Period of the egg
2. Extends from the time of fertilization until formation of the blastocyst
3. Implantation of the blastocyst into the uterine wall about one week after fertilization

From: unfertilized ovum to conception, to zygote, to 1st mitotic division, to 2-cell stage, to 16-cell morula, to 58-cell blastocyst, to 107-cell blastocyst, to the uterine wall

Question 7

What is the embryonic period?

Answer 7

1. Starts at the end of the first week of gestation, after implantation is initiated
2. Ends at the end of the 8th week (56 day)

*Organs form from 3 primary germ tissues

Question 8

What is the Fetal period?

Answer 8

1. Period characterized by rapid growth of the fetus and functional maturation of its organ systems
2. From weeks 9 to 38 after conception

*Organs grow in size and complexity

Question 9

What are 3 major stages of embryonic development?

Answer 9

1. Zygote
2. Morula
3. Blastocyst

Question 10

What is a Gametogenesis?

Answer 10

The formation of the gametes, the egg, and sperm

Question 11

What is Fertilization?

Answer 11

The joining of the gametes to form the zygote

Question 12

What is Cleavage?

Answer 12

1 A series of rapid cell divisions that result first in the formation of the morula (individual blastomeres)

2. Then the morula enters the uterine cavity for the formation of the blastocyst
3. During cleavage, the zygote is within the zona pellucida

Question 13

What is Gastrulation?

Answer 13

The rearrangement of cells in the embryonic region of the implanted blastocyst into 3 primary germ layers to form the embryonic disc

Question 14

What are the 3 germ layers?

Answer 14

1. Ectoderm
2. Mesoderm
3. Endoderm

Question 15

What is Trophoblast?

Answer 15

Formed by the outer cell mass, which surrounds the inner cells and the blastocyst cavity

Question 16

What is the Organogenesis?

Answer 16

The formation of organ rudiments and organ systems

*Formation of the tube-within-a-tube body plan and organogenesis occurs at the same time

Question 17

What is the Formation of the tube-within-a-tube body plan?

Answer 17

1. Conversion, through body folding, of the embryonic disc into a C-shaped embryonic body
2. Consisting of an outer ectodermal tube (future skin) and inner endodermal tube (the gut tube)
3. With the mesoderm interposed between the two tubes

Question 18

What infectious agents influence teratogenes?

Answer 18

1. Rubella virus (Causes babies to have microcephaly, PDA, and cataracts )
2. Herpes simplex

*virus are able to travel through the umbilical cord

Question 19

What is Teratogenesis? (teratogenes)

Answer 19

The process by which congenital malformations are produced in an embryo or fetus

Question 20

What physical agents influence teratogenesis? (teratogenes)

Answer 20

1. X-rays (avoid on pregnant women)
2. Hyperthermia

*Spina bifida from the physical agent hyperthermia causes an open defect. (spinal cord doesn’t close and sticks out)

Question 21

What Chemical agents influence teratogenes?

Answer 21

1. Alcohol
2. Isotretinoin (Small and abnormal sharp ears/cleft palate; Rx used for Accutane)
3. Thalidomide (limb defects/heart malformation; Rx used for leprosy)
4. Aspirin (low birth rate/infant death)
5. Heavy caffeine (miscarriage/premature births)

Question 22

What is the duration of the fetal period?

Answer 22

1. Normal duration is 40 weeks after LMP
2. Or 38 weeks after fertilization

• Before 38 weeks: premature
• After 42 weeks: Post mature

Question 23

What is Nagele’s rule?

Answer 23

1. LMP+7days-3months

Question 24

What is the period for Infancy?

Answer 24

1. The first year after birth

* Younger than 1 month is known as neonate

Question 25

What is the period for childhood?

Answer 25

The period between infancy and puberty

Question 26

What is the period for puberty?

Answer 26

1. Period when humans develop procreation of the reproductive organs * women: age 8 * men: age 9

Question 27

What is the period for adulthood?

Answer 27

1. Between the ages 18 and 21 | * Ossification and growth are virtually completed during early adulthood (21 to 25 years old)

Question 28

What are 4 anatomical positions in a human?

Answer 28

1. Anterior (or ventral for fetus) 2. Posterior (Dorsal) 3. Superior (Cranial ) 4. Inferior (Caudal)

Question 29

What is induction?

Answer 29

1. Process of the interaction of the different types of tissue (mesenchyme and epithelium) 2. Includes an INDUCER and RESPONDER 3. The capacity to respond the signaling from the other tissues known as COMPETENCE

Question 30

What is competence in the induction process?

Answer 30

1. Activated by a competence factor | * Cell signaling is essential for induction

Question 31

What is the Paracrine Signaling?

Answer 31

1. Type of signaling from one cell to another where proteins synthesized by one cell diffuse short distances to interact with other cells. (diffusable proteins) * Cells release signals that affect nearby target cells * Includes a signaling molecule (the ligand) and a receptor

Question 32

What is the pathway for Paracrine signaling?

Answer 32

1. Ligand (inducer) binds to receptor 2. Activates enzymatic activity (kinase) that can phosphorylate other proteins 3. Chain reaction of phosphorylation activates transcription factor 4. The transcription factor activates or inhibits gene expression as it enters the nucleus

Question 33

What is Juxtacrine signaling?

Answer 33

1. Doesn't involve diffusable factors 2. A protein on one cell surface interacts with a receptor on an adjacent cell 3. Ligands in the ECM are secreted by one cell interaction with their receptors on neighboring cells 4. A direct transmission of signals from one cell to another by gap junctions

Question 34

What is GDFs?

Answer 34

1. The diffusable proteins responsible for paracrine signaling Growth differential factors (other name for paracrine factors)

Question 35

What is the Hedgehog signaling?

Answer 35

1. Three types: a. desert b. Indian c. sonic 2. "Master gene for embryogenesis 3. Contain multiple enhancer elements

Question 36

What are 4 types of signaling neurotransmitters?

Answer 36

1. Serotonin 2. GABA (or gamma amino butyric acid) 3. Epinephrine 4. Norepinephrine

Question 37

What is the pathway for Hedgehog signaling?

Answer 37

1. After translation the protein is cleaved and cholesterol is added to its C-terminus 2. The palmitic acid is added to its N-terminus and SHH becomes fully functional 3. It binds to its receptor patched (Ptc) 4. Removes an inhibition of the receptor-like protein Smoothened (Smo) 5. Smo simulates the GLI family of transcription factors that control expression of target genes

Question 38

What is the planar cell polarity pathway?

Answer 38

1. Reorganization of cells and cell sheets in the plane of tissue 2. Leads to the narrowing and elongation of tissues (convergent extension)

Question 39

What genes are involved in the Planar Cell Polarity Pathway?

Answer 39

1. WNT and its receptor FRIZZLED, CELSR, and VANGL that code transmembrane proteins 2. DISHEVELLED (DVL) that codes for a protein that acts through Rho and Rac kinases to affect the cytoskeleton and other gens that regulate cell movement

Question 40

What is the Notch pathway?

Answer 40

1. Notch transmembrane receptors bind to transmembrane ligands of the DSL family (Delta/Serrate/LAG-2) 2. There are 4 Notch family members and 5 transmembrane ligands (Jagged 1 and 2 and Delta 1 to 3) 3. Cleaved portion of the protein enters the nucleus directly and binds to a DNA-binding protein 4. This removes the inhibitory activity of the repressor and permits activation of the downstream genes *Takes place in the mesenchymal epithelial interactions

Question 41

What is Abortion?

Answer 41

1. Is a premature stoppage of development and expulsion of a conceptus from the uterus or expulsion of an embryo or fetus before it is viable

Question 42

What are the types of abortion?

Answer 42

1. Threatened abortion (treated and pregnancy can still occur) 2. Spontaneous abortion 3. Habitual abortion (The miscarriage of 3 or more consecutive pregnancies) 4. Induced abortion (medically induced before 20 weeks) 5. Completed abortion 6. Complete abortion 7. Missed abortion (retention of the embryo in the uterus after death) *Miscarriage (spontaneous abortion of a fetus and its membranes before the middle of the second trimester; 135 days)