2 Embryology

Question 1

Pre-embryonic period

Answer 1

First 2 weeks of development, fertilization of the zygote (2n) through morula(16n) to a multi-cellular (blastocyst) implants in the lining of the uterus.

Question 2

Beggining of embryonic period

Answer 2

3rd week Gasturation forming 3 primary germ layers through 8th week

Question 3

Fetal Period

Answer 3

9th week until birth

Question 4

Organogenesis

Answer 4

4th week to 8th week, three primary germ layers arrange themselves in ways that give rise to all organs in the body.

Question 5

Cleavage

Answer 5

2n-blastocyst

Question 6

phase after blastocyst

Answer 6

gastrulation which is implantation (3rd week) to formation of the germ layer.

Question 7

embryogenesis period from when to when.

Answer 7

Beginning of zygote (2n) ending week 8 embryonic period.

Question 8

gametogenesis

Answer 8

maturation of the testes or ovaries for the production of sex cells.

Question 9

oocyte

Answer 9

egg from female in the widest part of the uterine tube called the ampulla.

Question 10

Capacitation

Answer 10

A period of conditioning that takes place before fertilization of the secondary oocyte is possible.

Question 11

acrosome

Answer 11

Is a membranous cap at the dead of the sperm containing digestive enzymes which can break down the protective layers surrounding the oocyte.

Question 12

Corona Radiata Penetration

Answer 12

Is the outer layer to the secondary oocyte which the sperm pushes through using it’s flagella. Then the spearm reaches the Zona Pellucida.

Question 13

Zona Pellucida Penetration

Answer 13

The sperm uses digestive enzymes released from the acrosome (head) of the sperm.

Question 14

Polyspermy

Answer 14

two sperm enter the same second oocyte. It is immediately fatal.

Question 15

cytotrophoblast

Answer 15

inner layer of the trophoblast

Question 16

syncytiotrophoblast

Answer 16

is the outer layer of the trophoblast

Question 17

trophoblast

Answer 17

outer cell layer covering the blastocyst that will allow the embryo to receive nourishment from the mother.

Question 18

Embryoblast

Answer 18

inner cell mast is a tightly packed group of cells located only within one side of the blastocyst.

Question 19

Blastocycst

Answer 19

The pre-embryo becomes a blastocyst in the uterine lumen prior to implantation (days 5-7)

Question 20

Formation of the Ovum

Answer 20

Once the nucleus of the sperm enters the secondary oocyte, the secondary oocyte completes the second meiotic division and forms an ovum.

Question 21

bilaminar germinal disc, or blastodisc.

Answer 21

By day 8, the cells of the embryoblast begin to differentiate into two layers. A layer of small, cuboidal cells adjacent to the blastocyst cavity is termed the hypoblast layer, and a layer of columnar cells adjacent to the amniotic cavity is called the epiblast layer.

Question 22

yolk sac

Answer 22

yolk sac is the first extraembryonic membrane to develop. It is formed from and continuous with the hypoblast layer. In humans, it does not store yolk as it does in eggs of birds and reptiles, but it is an important site for early blood cell and blood vessel formation

Question 23

amnion

Answer 23

amnion (am′nē-on; amnios = lamb) is a thin membrane that is formed from and continuous with the epiblast layer. The amnion eventually encloses the entire embryo in a fluid-filled sac called the amniotic cavity to protect the embryo from desiccation (drying out). The amniotic membrane is specialized to secrete the amniotic fluid that bathes the embryo.

Question 24

chorion

Answer 24

The chorion (kōr′ē-on; membrane covering the fetus) is the outermost extraembryonic membrane and is formed from both the rapidly growing cytotrophoblast cells and syncytiotrophoblast. These cells blend with the functional layer of the endometrium and eventually form the placenta, the site of exchange between the embryo and the mother.

Question 25

placenta

Answer 25

•Exchange of nutrients, waste products, and respiratory gases between the maternal and fetal bloodstreams •Transmission of maternal antibodies (immune system substances that target viruses or bacteria) to the developing embryo or fetus •Production of hormones (primarily estrogen and progesterone) to maintain and build the uterine lining

Question 26

pronuclei

Answer 26

Following the completion of meiosis, the nucleus of the sperm and the nucleus of the ovum are called pronuclei (pro = before, precursor of) because they have a haploid number of chromosomes. These pronuclei come together and fuse, forming a single nucleus that contains a diploid number (23 pairs) of chromosomes. The single diploid cell formed is the zygote.

Question 27

Week 3, Gastrulation

Answer 27

3 germlayers are formed, once formed it may be called an embryo.

Question 28

Primary Germ Layers

Answer 28

Ectoderm, mesoderm, endoderm.

Question 29

Cephalocaudal folding

Answer 29

Cephalocaudal (sef′ă-lō-kaw′dăl) folding occurs in the cephalic (head) and caudal (tail) regions of the embryo. Essentially, the embryonic disc and amnion grow very rapidly, but the yolk sac does not grow at all. This differential growth causes the head and tail regions to fold on themselves.

Question 30

Transverse folding

Answer 30

Transverse folding (or lateral folding) occurs when the left and right sides of the embryo curve and migrate toward the midline. As these sides come together, they restrict and start to pinch off the yolk sac. Eventually, the sides of the embryonic disc fuse in the midline and create a cylindrical embryo. Thus, the ectoderm is now solely along the entire exterior of the embryo, and the endoderm is confined to the internal region of the embryo. As this midline fusion occurs, the yolk sac pinches off from most of the endoderm (with the exception of one small region of communication called the vitelline duct).

Question 31

teratogens

Answer 31

substances that can cause birth defects or the death of the embryo. Teratogens include alcohol, tobacco smoke, drugs, some viruses, and even some seemingly benign medications, such as aspirin.

Question 32

Ectoderm

Answer 32

Epidermis of skin and epidermal derivatives(hair, nails, sweat glands, mammary glands)Nervous tissue, pituitary gland, Adrenal gland, Enamel of teeth, Lens of eye

Question 33

Endoderm

Answer 33

All tissue of the body. Epithelial lining of respiratory tract, GI tract, urinary tract, reproductive tract, tympanic cavity, auditory tube. Liver, Gull bladder, Pancreas, Palatine tonsils, Thyroid glands, Thymus

Question 34

Mesoderm

Answer 34

Dermis of skin, Epithelial lining of blood vessels, lymph vessels, serous membranes. Muscle tissue, Adrenal cortex, Heart, Kidneys and ureters, internal reproductive organs, spleen.

Question 35

Paraxial mesoderm

Answer 35

is found on both sides of the neural tube. The paraxial mesoderm then forms somites (sō′mīt; soma = body), which are blocklike masses responsible for the formation of the axial skeleton, most muscle (including limb musculature), and most of the cartilage, dermis, and connective tissues of the body

Question 36

intermediate mesoderm

Answer 36

•Lateral to the paraxial mesoderm are cords of intermediate mesoderm, which forms most of the urinary system and the reproductive system.

Question 37

lateral plate mesoderm

Answer 37

•The most lateral layers of mesoderm on both sides of the neural tube remain thin and are called the lateral plate mesoderm. These give rise to most of the components of the cardiovascular system, the lining of the body cavities, the thoracic and abdominal body walls, and all the connective tissue components of the limbs.

Question 38

head mesenchyme (mes′eng-kīm),

Answer 38

The last region of mesoderm, called the head mesenchyme (mes′eng-kīm), forms connective tissues and musculature of the face.

Question 39

congenital anomaly

Answer 39

A malformation or deformity present at birth

Question 40

ectopic pregnancy

Answer 40

A pregnancy in which the embryo implants outside the uterus; commonly occurs in the uterine tube, in which case it is called a tubal pregnancy.

Question 41

amniocentesis

Answer 41

This procedure is usually performed during the fourth month of pregnancy. About 5 to 10 milliliters (mL) of amniotic fluid (the fluid surrounding the developing fetus) are collected from within the mother’s uterus using a hypodermic needle.

Question 42

teratology

Answer 42

Branch of science concerned with congenital malformations.

Question 43

What is gastrulation?

Answer 43

The embryonic period begins with the establishment of the three primary germ layers through the process of gastrulation. Gastrulation produces a trilaminar embryonic disc that contains three primary germ layers: endoderm, mesoderm, and ectoderm.

Question 44

Neurulation

Answer 44

The process of nervous system formation from the ectoderm is called neurulation.