Exam 3 - Development Anatomy Lec Flashcards

These flashcards cover early embryonic development, including gastrulation, neurulation, heart formation, embryo folding, and placental development.

What are the two layers of the bilaminar disc and when does it form?

The bilaminar disc is composed of the epiblast (upper layer) and the hypoblast (lower layer), forming during the second week of development.

What are the three germ layers of the trilaminar disc and when does it form?

The trilaminar disc contains the ectoderm, mesoderm, and endoderm, which form during the third week of development during gastrulation.

What is gastrulation?

Gastrulation is the process where the two-layered bilaminar disc is reorganized into the three-layered trilaminar disc, which later forms all tissues and organs.

How does gastrulation help establish the axis of the body?

It marks the locations for the head and tail (anterior-posterior), back and front (dorsal-ventral), and left and right.

Which specific structures initiate the process of gastrulation?

The primitive streak (a linear groove on the epiblast surface), the primitive node, and the blastopore.

What is the primitive streak and what is its lifespan?

The primitive streak is a thick band of cells on the epiblast surface that forms during the third week and is a temporary structure lasting until the fourth week.

What congenital malformation can occur if the primitive streak remains until birth?

It can lead to a teratoma, which arises from leftover pluripotent cells of the primitive streak.

What is the fate and timing of the oropharyngeal membrane breakdown?

It breaks down in the fourth week to form the mouth; it is located at the head end of the embryo in front of the primitive streak.

What is the fate and timing of the cloacal membrane breakdown?

It breaks down in the seventh week to form the anus and openings of the urinary and genital tracts; it is located at the tail end behind the primitive streak.

What is neurulation?

Neurulation is the process that forms the neural tube, which eventually becomes the brain and spinal cord.

What role does the mesoderm play in neurulation?

The mesoderm forms the notochord, which signals the ectoderm to become the neural plate.

How is the neural tube formed?

The edges of the neural plate fold to create neural folds, which then join together to form the neural tube.

What are the derivatives of the neural tube and the neural crest?

The neural tube forms the Central Nervous System (CNS), including the brain and spinal cord, while the neural crest forms peripheral nerves and other tissues.

What are the three types of neural tube defects described in the notes?

1) Spina bifida (spinal cord doesn’t close completely); 2) Anencephaly (brain and skull do not develop normally); 3) Encephalocele (brain tissue pushes through skull opening).

Which specific layer is responsible for heart development?

The splanchnic layer of the lateral plate of the mesoderm.

In heart development, what does the Truncus arteriosus become?

The aorta and pulmonary artery.

In heart development, what does the Bulbus cordis become?

The right ventricle.

In heart development, what do the Primitive ventricle and Primitive atrium become?

The Primitive ventricle becomes the left ventricle, and the Primitive atrium becomes the right and left atria.

What are the two types of embryo folding and their importance?

Lateral folding joins the heart tubes and forms the body wall/gut; Head folding moves the heart into the chest and places it in the pericardial cavity.

Why is the embryo called a fetus after 9 weeks of development?

Because all major body organs and basic structures have formed, shifting focus from organ formation to refinement, maturation, and rapid growth in size/weight.

What is the vitelline duct and when does it disappear?

A temporary structure connecting the yolk sac to the developing midgut; it naturally disappears by the 5th-9th week of pregnancy.

What problems can arise if the vitelline duct does not resolve after birth?

Umbilical polyps and Meckel’s Diverticulum.

What is a blighted ovum?

An unhealthy pregnancy defect where a gestational sac is present on an ultrasound but no embryo is inside.

How is the placenta formed from the trophoblast?

The trophoblast forms finger-like projections that grow into the uterus.

Which vessel carries oxygenated blood to the fetus?

The umbilical vein.

Define the placenta abnormalities: previa, abruption, and accreta.

Placenta previa: placenta covers the cervix; Placental abruption: placenta separates from the uterus wall too early; Placenta accreta: placenta grows too deeply into the uterus.

What is the risk if the placenta is not removed after birth?

It can cause severe bleeding (hemorrhage) and may require the mother to undergo surgery.

When are the yolk sac and placenta formed?

Both begin forming during the second week of development

How is the yolk sac formed?

The yolk sac forms from hypoblast cells that extends into the blastocyst

How is the placenta formed?

The placenta forms when the trophoblast implants into the uterine wall and develops chorionic villi

What is the function of the yolk sac?

It provides nutrients to the embryo during early development before the placenta forms.

What is the function of the placenta?

It supplies the fetus with oxygen and nutrients and removes waste products.

Why is the gestational sac important during an ultrasound?

It is the first sign of pregnancy, confirms the pregnancy is inside the uterus, and shows the pregnancy is developing normally.

Why is the yolk sac important during an ultrasound?

It shows that the early pregnancy is developing and provides nutrients and oxygen to the embryo before the placenta forms.

What is an anterior placenta?

A placenta attached to the front of the uterus

What is a posterior placenta?

A placenta attached to the back of the uterus.