2 Embryology Flashcards
Pre-embryonic period
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.
Beggining of embryonic period
3rd week Gasturation forming 3 primary germ layers through 8th week
Fetal Period
9th week until birth
Organogenesis
4th week to 8th week, three primary germ layers arrange themselves in ways that give rise to all organs in the body.
Cleavage
2n-blastocyst
phase after blastocyst
gastrulation which is implantation (3rd week) to formation of the germ layer.
embryogenesis period from when to when.
Beginning of zygote (2n) ending week 8 embryonic period.
gametogenesis
maturation of the testes or ovaries for the production of sex cells.
oocyte
egg from female in the widest part of the uterine tube called the ampulla.
Capacitation
A period of conditioning that takes place before fertilization of the secondary oocyte is possible.
acrosome
Is a membranous cap at the dead of the sperm containing digestive enzymes which can break down the protective layers surrounding the oocyte.
Corona Radiata Penetration
Is the outer layer to the secondary oocyte which the sperm pushes through using it’s flagella. Then the spearm reaches the Zona Pellucida.
Zona Pellucida Penetration
The sperm uses digestive enzymes released from the acrosome (head) of the sperm.
Polyspermy
two sperm enter the same second oocyte. It is immediately fatal.
cytotrophoblast
inner layer of the trophoblast
syncytiotrophoblast
is the outer layer of the trophoblast
trophoblast
outer cell layer covering the blastocyst that will allow the embryo to receive nourishment from the mother.
Embryoblast
inner cell mast is a tightly packed group of cells located only within one side of the blastocyst.
Blastocycst
The pre-embryo becomes a blastocyst in the uterine lumen prior to implantation (days 5-7)
Formation of the Ovum
Once the nucleus of the sperm enters the secondary oocyte, the secondary oocyte completes the second meiotic division and forms an ovum.
bilaminar germinal disc, or blastodisc.
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.
yolk sac
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
amnion
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.
chorion
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.
placenta
•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
pronuclei
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.
Week 3, Gastrulation
3 germlayers are formed, once formed it may be called an embryo.
Primary Germ Layers
Ectoderm, mesoderm, endoderm.
Cephalocaudal folding
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.
Transverse folding
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).
teratogens
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.
Ectoderm
Epidermis of skin and epidermal derivatives(hair, nails, sweat glands, mammary glands)Nervous tissue, pituitary gland, Adrenal gland, Enamel of teeth, Lens of eye
Endoderm
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
Mesoderm
Dermis of skin, Epithelial lining of blood vessels, lymph vessels, serous membranes. Muscle tissue, Adrenal cortex, Heart, Kidneys and ureters, internal reproductive organs, spleen.
Paraxial mesoderm
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
intermediate mesoderm
•Lateral to the paraxial mesoderm are cords of intermediate mesoderm, which forms most of the urinary system and the reproductive system.
lateral plate mesoderm
•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.
head mesenchyme (mes′eng-kīm),
The last region of mesoderm, called the head mesenchyme (mes′eng-kīm), forms connective tissues and musculature of the face.
congenital anomaly
A malformation or deformity present at birth
ectopic pregnancy
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.
amniocentesis
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.
teratology
Branch of science concerned with congenital malformations.
What is gastrulation?
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.
Neurulation
The process of nervous system formation from the ectoderm is called neurulation.
