Human Embryology Exam 1 Review

Flashcards based on Human Embryology Exam 1 Review Lecture Notes

Where do primordial germ cells initially arise?

Epiblast region of an early embryo, near the posterior primitive streak

Where do primordial germ cells migrate to first?

Endoderm of the hindgut

What unique alterations occur during meiosis I?

Germ cell has 4 daughter cells

What unique alterations occur during meiosis II?

Reduces chromosome number by half

Describe the DNA content of a diploid germ cell.

2N (46 chromosomes)

Describe the DNA content of a haploid germ cell.

1N (23 chromosomes)

Where does spermatogenesis take place?

Seminiferous tubules of the testes

When does spermatogenesis begin?

Puberty

What are the parts of a mature sperm?

Tail, head, acrosomal cap, gunk layer

What is the role of the sperm tail?

Motility

What is the role of the acrosomal cap?

Contains enzymes to attach to the egg

What meiotic stage are spermatogonial cells in?

Haploid 2N

What meiotic stage are primary spermatocytes in?

Diploid 4N (Prophase 1)

What meiotic stage are secondary spermatocytes in?

Haploid 1N (meiosis 2)

What is spermatogenesis?

The whole process of male sperm division

What is spermiogenesis?

The final step of spermatogenesis, creating mature spermatozoa

Which pituitary hormones play a role in the menstrual cycle?

LH (luteinizing hormone) and FSH (follicle stimulating hormone)

Which ovarian hormone helps follicle development and endometrial proliferation?

Estrogen

Which ovarian hormone prepares the endometrium for implantation?

Progesterone

What meiotic stage are oogonia in?

Diploid 2N

What meiotic stage are primary oocytes in?

Diploid 4N

What meiotic stage are secondary oocytes in?

Haploid 2N

What meiotic stage are definitive oocytes in?

Haploid 1N

How does the timing of oogenesis differ from spermatogenesis?

Oogenesis begins meiosis before puberty

What does an oocyte look like before fertilization?

Contains a zona pellucida and corona radiata

Where does an oocyte reside in the fallopian tube?

Ampulla

When and where does capacitation occur?

At the oocyte

What is the function of the acrosome cap?

Allows access into the cell of the oocyte

What part of the spermatozoon enters the oocyte?

Head

How is the final step in oogenesis regulated?

Penetration of the oocyte during fertilization

What is a block to polyspermy?

Prevention of multiple sperm fertilizing an egg

What is the function of cortical granules?

Help cause a reaction with the sperm head to occur.

What is the zona reaction?

Results with the corona radiata to fly off

What is the difference between postfertilization age and LNMP?

LNMP is post-fertilization age plus 2 weeks

What is a morula?

A 16-cell embryo

When does the morula form?

Roughly 3.5 days

What is a blastocyst?

Roughly 4 days in and has 32 cells

What is the fate of the inner cell mass?

Becomes the embryoblasts

What is the fate of the outer cell mass?

Becomes the trophoblasts

What is the zona pellucida?

Outer edge of the cell that protects the oocyte

What is hatching?

When zona breaks open

When does implantation occur?

Roughly on day 6-7

What role is played by proliferation of hypoblast?

Helps create the primary yolk sac.

When is the primary yolk sac formed?

Roughly on day 10

What is the fate of the primary yolk sac?

To collapse and is absorbed by the embryo

Describe the embryo at the end of the first week.

A blastocyst beginning to attach to endometrial lining

Describe the embryo at the end of the second week.

A two-layered disc with the head end indicated by the prochordal plate and the tail end indicated by the first indication of the primitive streak

What are the major milestones of the first week?

Implantation, transforming of trophoblast cells into cytotrophoblasts

What are the major milestones of the second week?

Formation of connecting stalk, primitive streak forming

What is the prochordal plate?

A thickened region of the endoderm cells on the anterior side

What will the prochordal plate become?

The oropharyngeal membrane or the mouth

When are the major axes of the body formed?

During the second week

What is the bilaminar germ disc?

Composed of the epiblasts and the hypoblast layers

What structures comprise the primitive streak?

It's the epiblasts cells that become thickened

What role does the primitive streak play in gastrulation?

Starts the formation of the different germ layers

What germ layer do epiblasts become?

Ectoderm and mesoderm

What germ layer do hypoblasts become?

Endoderm

What and where is the connecting stalk?

Located at the top, opening where not mesoderm is located

What and where is the cloacal membrane?

The exit, composed of 2 layers- no mesoderm

In what order are specific tissues produced by gastrulation?

Endoderm, Mesoderm then ectoderm

From what structure does the notochord arise?

The axial mesoderm

What will paraxial mesoderm give rise to?

Muscles and axial skeleton

What will intermediate mesoderm give rise to?

Urogenital system

What will lateral plate mesoderm give rise to?

Many organ systems but the circulatory system

What is the allantoic diverticulum?

The allantois which is the trash or waste bin where our feces and urine would go in the end

What is the neural plate?

A thickened section of the ectoderm

When is the neural plate formed?

During week 3 roughly day 16

What is the intraembryonic coelom?

Fluid within the mesoderm on the lateral plate

When do heart tubes form?

Around day 18-19

What are the three major veins in the 3-week embryo?

The umbilical, cardinal and the vitelline vein

What major change happens to the intraembryonic coelom in the 3rd week?

Invades the lateral plate of mesoderm

What are the major milestones of the third week?

Segmentation has begun in the somite’s and the neural crest clumps. Circulation begins. Intraembryonic coelom has begun invading inside the lateral plate.

What is the process of neurulation?

The process that creates the neural tube

What is a somite?

Apart of the mesoderm on the paraxial part

What does a somite become?

Vertebral column, skeletal muscle and the dermis

What is a sclerotome?

Forms the vertebrae, ribs and intervertebral discs

What is a dermomyotome?

Dorsal part of a somite that becomes the dermis and skeletal muscles

What is a dermatome?

Helps makes the dermis as well and surrounds the neural tube and makes the meninges (spinal)

What is a myotome?

Makes muscular tissue, composed in epaxial and hypaxial

Where do neural crest cells arise?

Between the border of the neural plate and the ectoderm

What are the spinal curvatures?

Lordosis and kyphosis

What is a meningotome and what does it form?

What the meningies become

What is a syndetome and what does it form?

Forms tendons and cartilage in same segment

What and where is the septum transversum?

Located right above the heart tubes

What will septum transversum become?

A divider between a few things but ends up as the diaphragm

Describe the embryo in the middle of the 4th week.

Has head shaped amniotic cavity, yolk sac had become more circular at bottom but rises higher. Oropharyngeal membrane becomes vertical. Cloacal membrane also becomes vertical.

What is the caudal eminence/tail bud?

Leftover of the primitive streak

What is the vitelline duct?

Gut tube

What are the layers of the umbilical cord?

The layers are the yolk sac, the mesoderm, endoderm, and ectoderm

What does viscerial pericardium do?

Wrap heart

What does Parietal pericardium do?

Attaches to the chest

What is the laryngotracheal diverticulum?

Larynx and trachea

What are the pleuroperitoneal membranes?

Separates the pleural cavity from the peritoneal cavity by fusing the septum transversum and the mesentery of the esophagus

Which dermomyotomes invade the lateral portions of the diaphragm?

Hypaxial

What is the chorionic cavity?

The fluid filled cavity that surrounds the embryo during early pregnancy, made from trophoblast and extraembryonic mesoderm

What are the different types of chorion?

Chorion Frondosum and Chorion leave

What are the different types of decidual?

Decidual Balis, Decidual capsularis, and Decidual parietalis

What layers form the placenta?

Amnion and Chorion

What is the difference between a primary, secondary and tertiary villus?

Differ in the presence and development of mesoderm and blood vessels

What is the fate of the cloacal membrane?

Urogenital and anal membrane