Embryology theory

Winter final 26

Which compartment of the blastocyst forms the fetus?

Embryoblast

Which layer of the early embryo contacts the endometrium?

Amnion

The adenohypophysis is derived from which germ layer?

Ectoderm

Describe the path of sperm during insemination.

Vagina, Cervix, Uterus, Uterine Tubes

The heart and blood vessels are derived from which germ layer?

Lateral plate mesoderm

Which structure forms the lacunae during implantation?

Syncytiotrophoblast

On which embryonic structure is the olfactory placode located?

Frontonasal prominence

What is the name of the inner mucosal lining of the uterus?

Endometrium

What is the definition of insemination?

Deposit of sperm into the female reproductive tract

The nephrogenic cords originate from which germ layer?

Intermediate mesoderm

Which type of chorionic villi penetrates most deeply into the endometrium?

Tertiary villi

During which week does notochord formation occur?

Third week

What are teratogens?

Agents that cause congenital malformations

Which structure does NOT originate from endoderm?

Heart and blood vessels

What structures are contained within the definitive umbilical cord?

Two umbilical arteries and one umbilical vein

What does gastrulation establish?

The three primary germ layers (ectoderm, mesoderm, endoderm)

The epithelium of the body's serous cavities (peritoneal, pleural, pericardial) originates from which mesoderm?

Lateral plate mesoderm

Which seminal fluid component raises pH and activates sperm?

Seminal vesicle fluid

What happens to cell size during cleavage?

Cells do not grow; they divide to become smaller

What is a major risk of a tubal (ectopic) pregnancy?

Fallopian tube rupture

How many chromosome pairs do primordial germ cells contain?

23 pairs (46 total)

What are conjoined twins fused at the head called?

Craniopagus

What do sclerotomes differentiate into?

Bone and cartilage surrounding the notochord

Which cells of spermatogenesis have bivalent chromosomes?

Primary spermatocytes (during meiosis I)

What are the two layers of the bilaminar disc?

Epiblast and Hypoblast

In which cell are cortical granules located?

Oocyte (in the peripheral cytoplasm)

Preimplantation genetic diagnosis typically analyzes which cells?

Blastomeres

What is the most medially located part of the intraembryonic mesoderm?

Paraxial mesoderm

What is the approximate rate of abnormal blastocysts?

20-30%

What is the typical volume of seminal fluid in a healthy ejaculate?

2-5 mL (Note: corrected from original 0.5-1mL, which is too low)

Which process is associated with the sperm's acrosomal reaction?

Fertilization / Penetration of the zona pellucida

Where does initial hematopoiesis occur?

Yolk sac (extravascular, then intravascular)

During cleavage, the dividing cells undergo what type of cell division?

Mitosis

Somites differentiate into all of the following EXCEPT?

Nephrotome

On what embryonic day do the endocardial heart tubes form?

Approximately day 19

Trisomy and monosomy are most often caused by what meiotic error?

Nondisjunction

What is the primary role of the notochord?

Serves as the basis for the axial skeleton

What type of tissue forms the core of the umbilical cord?

Mucous connective tissue (Wharton's jelly)

What structure forms the exocoelomic (Heuser's) membrane and cysts in week 2?

Hypoblast (of the yolk sac)

What is a primary function of the yolk sac?

Site of early blood cell formation (hematopoiesis)

The somatopleure and splanchnopleure are derived from which mesoderm?

Lateral plate mesoderm

Where do the first blood cells originate?

Yolk sac

Gastrulation begins at the start of which week?

Third week

What is the typical age range for menopause?

45-55 years

What is present in the extraembryonic cavity during the second week?

Exocoelomic (chorionic) cysts

What hormones are used to stimulate ovaries in IVF?

Gonadotropins (FSH/LH)

On which day does the posterior neuropore close?

Day 27-28

Which embryonic layer contacts the parietal hypoblast?

Cytotrophoblast

Which germ layer gives rise to the epiblast?

The epiblast is the layer; it doesn't "generate" another layer here.

Primary chorionic villi originate from which layer?

Cytotrophoblast

What structure lies ventral to (under) the neural tube?

Notochord

How long does sperm capacitation take in the female tract?

Approximately 5-10 hours

What is the histological classification of the human placenta?

Haemochorial

On which days does allantois formation begin?

Days 15-16

When does the secondary oocyte complete meiosis II?

At fertilization

What is the cellular composition of the hypoblast on day 8?

Small cuboidal cells

Which layer forms the amniotic cavity?

Epiblast

How long after fertilization does the first cleavage occur?

Approximately 24-30 hours

What forms the primitive endothelial cells?

Mesodermal cells lining the yolk sac (angioblasts)

The paraxial mesoderm segments into structures called what?

Somites

Gastrulation begins with the formation of what structure?

Primitive streak

Trophoblastic overgrowth without an embryo leads to what condition?

Hydatidiform mole (Molar pregnancy)

What is the correct developmental sequence for chorionic villi?

Primary (cytotrophoblast core) -> Secondary (mesoderm core) -> Tertiary (vascularized)

Which pharyngeal arch forms the mandible?

First pharyngeal arch

What structure forms at the cranial end of the primitive streak?

Primitive node (Hensen's node)

Cleavage begins when the zygote reaches how many cells?

2 cells (after the first division)

Which structures originate from endoderm?

Lining of GI tract, respiratory tract, urinary bladder, urethra, and associated glands (liver, pancreas, thyroid, thymus).

What are conjoined twins fused at the thorax called?

Thoracopagus

A somite differentiates into which components?

Dermatome, Myotome, Sclerotome, Syndetome

Turner syndrome is characterized by what chromosome anomaly?

45, X (Monosomy X)

How is the outermost layer of the embryonic mesoderm designated?

It is not "ectoderm." The intraembryonic mesoderm has paraxial, intermediate, and lateral plate regions.

What is the relationship of the umbilical arteries to the urinary bladder?

They arise from the internal iliac arteries and pass alongside the bladder.

Which tissues are derived from ectoderm?

Epidermis, nervous system (CNS & PNS), pigment cells.

What is the outermost layer of the pre-implantation embryo called?

Trophoblast

What are the two layers of the endometrium?

Stratum functionalis (sheds) and Stratum basalis (regenerates).

How long is a secondary oocyte viable for fertilization?

12-24 hours after ovulation

How many cavities are present in the conceptus at the end of week 2?

Two (Amniotic cavity and Chorionic cavity/extraembryonic coelom)

What is a normal sperm concentration (million/mL)?

15 million/mL or more

Which testicular cells produce testosterone?

Leydig (interstitial) cells

Which pole of the blastocyst implants into the endometrium?

Embryonic pole

The definitive ectoderm is formed by which layer of the bilaminar disc?

Epiblast

During which meiotic prophase I stage does crossing over occur?

Pachytene

What is the fertile window for conception?

The 5 days before ovulation and the day of ovulation.

What structure forms from the dorsal tips of the neural folds?

Neural crest cells

Spermatogonia divide to produce which cell type?

Primary spermatocytes

From which layer is the chorion derived?

Extraembryonic mesoderm and trophoblast

What is the purpose of amniocentesis?

Prenatal diagnosis of chromosomal and genetic disorders.

What are the cells of the morula called?

Blastomeres

When does implantation begin?

Day 6-7 after fertilization

How many chromosomes does a fertilized egg (zygote) have?

46 (23 pairs)

What are the maternal and fetal components of the placenta?

Maternal: Decidua basalis. Fetal: Chorionic plate and villi.

The cranial end of the primitive streak enlarges to form the what?

Primitive node

What is the main risk of a tubal pregnancy for the mother?

Internal hemorrhage from tubal rupture

The embryoblast differentiates in week 2 to form what structure?

Bilaminar germ disc (Epiblast & Hypoblast)

Which compartment of the blastocyst forms the placenta?

Trophoblast

How long does sperm migration to the egg typically take?

Minutes to hours, but capacitation takes longer.

When do primordial germ cells migrate to the gonadal ridges?

During weeks 4-6 of development

Which step is part of a standard IVF procedure?

Ovarian stimulation, egg retrieval, fertilization in lab, embryo transfer.

Which are considered embryonic membranes?

Amnion, Chorion, Yolk Sac, Allantois.

What is a primary chorionic villus composed of?

A core of cytotrophoblast