Development

What are the four parts of sperm?

Acrosome, Head, Neck, Flagellum.

What is the function of the acrosome in sperm?

Breaks through zona pellucida to connect with the egg and prevents cross-species fertilization.

What does the head of the sperm contain?

The nucleus.

What is the purpose of the neck of the sperm?

Contains many mitochondria to power the tail.

What is the function of the flagellum in sperm?

Provides mobility.

What occurs during the zygote stage?

The zygote is the single, fertilized cell formed immediately after the sperm and egg fuse.

What happens during the cleavage stage?

Rapid mitotic cell divisions occur without an increase in overall size, producing smaller cells called blastomeres.

What characterizes the morula stage?

A compact, solid ball of cells (around 16–32 cells) formed after several rounds of cleavage.

What is a blastula?

Hollow ball stage of cleavage that surrounds a cavity called the blastocoel.

What is the role of the trophoblast?

The outer cell layer of the blastocyst that develops into the placenta.

What is the function of the embryoblast?

The inner cell mass of the blastocyst that develops into the embryo.

How does implantation occur?

The trophoblast invades the endometrium, which then grows around it.

What is the role of the primitive streak?

It helps differentiate cells; mesoderm and endoderm arise from this structure.

What happens during gastrulation?

The embryo folds in on itself, forming the three tissue layers: endoderm, mesoderm, and ectoderm.

How does neurulation occur?

The neural plate forms from ectoderm and invaginates to close off and form the neural tube.

What does the endoderm develop into?

Lining of the gut and organs like the lungs, liver, and pancreas.

What does the ectoderm form?

Outer structures like epidermis, glands, hair, and part of the CNS.

What tissues do the mesoderm develop into?

Urogenital organs, dermis of skin, bone, and muscles.

What is the role of the yolk sac?

Provides nutrients to the embryo.

What function does the amnion serve?

Provides an aquatic environment and cushioning for the embryo.

What is the role of the allantois?

Provides storage for nitrogenous waste.

What does the chorion do?

Provides gas exchange for the embryo.

Which structures make up the placenta?

Chorion and allantois.

What happens during the embryo stage?

Structures form and blood bypasses lungs and liver; development occurs between 2-8 weeks.

What major developments occur around 4 weeks in the embryo stage?

Head, jaw, heart, blood, and limbs begin to form.

What occurs in the fetal stage?

Additional development of organs and features, and systems mature.

What hormonal changes affect parturition?

Positive feedback mechanism involving prostaglandins and oxytocin.

What does the ductus venosus do?

Bypasses liver, shunting blood directly to the heart from placenta.

What happens if the ductus venosus fails to close after birth?

Forms a partosystemic shunt (PSS).

What is the function of the foramen ovale?

Connects the right and left atria to bypass the lungs.

What happens if the foramen ovale fails to shut after birth?

A patent foramen ovale forms, leading to a heart murmur.

What does the ductus arteriosus connect?

Connects the pulmonary artery and aorta to shunt blood away from lungs.

What are potential complications if the ductus arteriosus fails to shut after birth?

A patent ductus arteriosus (PDA) occurs.