Cartões: Human Embryology | Quizlet

Critical period

In human development (3-8 weeks) where the embryo is most susceptible to the formation of congenital anomalies from teratogens

Critical dose

Exposure and gene-environment interactions also influence the severity of and/or susceptibility to birth defects

Embryonic period

Zygote formation to the end of the 8th week
- Period of organogenesis

Fetal period

Beginning of the 3rd month to the end of intrauterine life
- No new creation of structures, just growth

What is the leading cause of infant death?

Birth defects

Birth defect categories

Genetic factors, environmental factors, multifactorial inheritance

Most and least common birth defect

Clubfoot (most), anencephaly (least)

Gametogenesis

Process by which primordial germ cells (PGCs) reduce the number of chromosomes and undergo cytodifferentiation to complete maturation

PGCs appear in the wall of the ___________ and begin migrating toward the posterior body wall to ____________________ (in biological parent)

yolk sac; developing gonads

How many spermatids are created from 1 PGC?

4 spermatids

How many oocytes (and polar bodies) are created from 1 PGC?

1 oocyte (and 3 polar bodies)

Spermatogenesis vs oogenesis

Spermatogenesis:

- Starts (& continues throughout life, so not a fixed number of primary spermatocytes) at puberty

- PGCs will stay dormant until puberty

Oogenesis:

- Mitosis stops when the fetus reaches 5 months gestation (fixed amount)

- Meiosis I begins at puberty and then arrests until ovulation; @ ovulation will enter MII and then arrest at metaphase. Will complete MII if fertilized

Capacitation

Process where glycoproteins and seminal proteins are removed from the sperm's acrosome
- Mediated by female genital tract substances

Sperm must undergo _________ to be able to fertilize the oocyte

Capacitation

In oogenesis, the first phase of meiosis begins in the 3rd-5th month in utero where it arrests in ____________ until _________

Prophase I (MI); puberty

What triggers the primary oocyte to resume meiosis I?

Surge of the luteinizing hormone during the beginning of puberty

Pituitary hormones

FSH and LH

Ovarian hormones

Estrogen and progesterone

Corpus luteum purpose

Produce progesterone and will be maintained through hCG during embryonic development (to prevent the shedding of the endometrium)

Zona pellucida function

Prevents polyspermy and protects the egg

Acrosomal enzyme function

The release allows sperm to penetrate the zona pellucida

Trophoblast cell function

Contact and implant into the endometrium
- Develop into the placenta

Chorionic villi function

Increase the surface area by which maternal and fetal blood flow through the placenta to exchange metabolites/gases

Phases of fertilization

1. Capacitation of sperm

2. Acrosomal enzyme release

3. Sperm penetrates the zona

4. Zona reacts (cortical granules release their contacts rendering the zona impenetrable to others)

5. Sperm and oocyte membranes fuse

6. Oocyte resumes meiosis II

When does cleavage occur?

24 hours after fertilization

Cleavage process

Subdivides the zygote, without increasing the size of the cell

- Zona intact

Morula stage

16-32 cells
- Travels into the uterine cavity, where the uterine fluid enters and pushes cells to one side of the egg
- Zona intact

Blastocystic cavity separates the blastocyst into an ____________ and ______________ cell mass

Inner; outer (a bilaminar disc)

- Now referred to as a blastocyst

When does the zona pellucida shed/hatch?

Late blastocystic stage (days 5-6)

- Before implantation

Early blastocysts contain...

Embryoblast (inner cell mass), zona pellucida, blastocystic cavity, trophoblasts

Late blastocysts contain...

Embryonic poke, blastocystic cavity, trophoblast, embryoblasts

Embryonic pole

Region to first make contact with endometrial epithelium (trophoblast specifically)

The blastocystic cavity will become...

Primary yolk sac

Trophoblast separates into...

Syncytiotrophoblast and cytotrophoblast

Embryoblast becomes...

Embryo proper
- Hypoblast and epiblast

When does implantation occur?

Day 7

Implantation (beginning)

Syncytiotrophoblasts pull the blastocyst into the uterine wall
- Hypoblast are ventral
- Epiblast are dorsal

Implantation (middle)

Syncytiotrophoblasts continue to pull the blastocyst into the uterine wall. The amniotic cavity is now present

Implantation (final)

On day 9, full implantation achieved
- Trophoblastic lacuna develop inside the syncytioblast, pulling the blastocyst closer to maternal glands
- Hypoblast signal extraembryonic endoderm formation by proliferating and pushing towards outside of the blastocyst

Trophoblastic lacuna function

Allow maternal blood to accumulate within the lacunae

What comprises 1° chorionic stem villi?

Extensions and the outer layer of the syncytiotrophoblasts

What tissue forms early embryonic vessels?

Splanchnic mesoderm

Blood cells are first supplied by the...

Yolk sac

What structures form the arterial system?

Aortic arches and paired dorsal aortae

Aortic arches wrap around the...

Foregut (arches)

What supplies the pharyngeal arches with blood?

Aortic arches

What tissue forms the aortic arches?

Mesoderm

Which aortic arches regress?

Aortic arches 1 & 2

Restructuring of the aortic arches depends on...

Breakdown of the left and right dorsal aortae between the 3rd and 4th arch

Blood traveling through the 3rd arch goes to the ________ region after tissue breakdown

Head

Blood traveling through the 4th and 6th arch goes to the ________ region after tissue breakdown

Trunk

3rd aortic arches remain connected to...

Left/right dorsal aorta and the aortic sac (3rd arch)

Proximal 3rd aortic arch forms

Common carotid arteries

Distal 3rd aortic arch forms

Part of the internal carotid

Left 4th aortic arch forms

Midportion of the arch of the aorta

Lower right 4th aortic arch disappears or stays?

Disappears

Right 4th aortic arch forms

Proximal right subclavian artery

Left 4th aortic arch remains connected to the...

Dorsal aorta and the aortic sac derivatives (4th arch)

Left 6th aortic arch forms

Proximal left pulmonary artery

Distal left 6th aortic arch forms

Ductus arteriosus

Right 6th aortic arch forms

Proximal right pulmonary artery

Ductus arteriosus

Carries oxygenated blood leftover from the placenta to fetal organs
- Useful for arterial compensation

Why do the recurrent laryngeal nerves change their course?

Distal 6th arch regresses and the 5th arch degenerates

Final position of recurrent laryngeal nerves

Left: Hooks under ligamentum arteriosum (a derivative of DA)
Right: Hooks under right subclavian artery

Vitelline vein artery fate

Maintained as a GI plexus of arterial vessels

Umbilical artery fate

Regress (umbilical artery)

Intersegmental arteries

Derivatives of the dorsal aorta
- Branches that supply 1 somite (and it's derivatives) then lose their connection

Patent ductus arteriosus

Failure of the ductus arteriosus to close after birth, resulting in an abnormal opening between the pulmonary artery and the aorta
- @ birth, inc PO2, increase leads prostaglandin E2 production to stop, close DA

Coarctation of the aorta

Narrowing of the aorta in the ductus arteriosus region (above or below)
- Theory: PO2 sensitive muscle cells of the DA migrate to aortic wall, at birth, when PO2 levels increase, aortic muscles contract in response, leads to narrowing

Double aortic arch

Abnormal persistence of the right dorsal aorta
- Result: Trachea and esophagus are trapped in a vascular ring

Umbilical vein gets blood from...

Placenta (blood supply for vein)

Vitelline vein gets blood from...

Yolk sac (blood supply for vein)

Cardinal veins get blood from...

Embryo proper (anterior + posterior)

Vitelline vein forms the...

- Ductus venosus

- Superior RVV makes inferior vena cava

- RVV below liver makes portal and superior mesenteric veins

Ductus venosus function

Shunts half of the oxygenated blood from the umbilical vein directly to the right atrium
- If not, liver would take too much oxygenated blood

Where is the ductus venosus located?

liver (location)

Left umbilical vein forms an anastomosis with the...

Ductus venosus (LUV)

Left anterior cardinal vein breaks down to form the ________________________ with the right anterior cardinal vein

Left brachiocephalic vein

Left brachiocephalic rein function

Shunts blood coming from the left side of the head to the right side
- Blood flow now entering the right side of the atrium

Right common cardinal vein and caudal right anterior cardinal vein form the...

Superior vena cava (what forms)

Posterior cardinal veins are replaced by...

Subcardinal, sacrocardinal, and supracardinal

Double Superior Vena Cava (Persistent Left Superior Vena Cava)

Inadequate anastomosis between the right and left anterior cardinal vein
- Persistence of a vessel on the left side that drains to the right atrium via coronary sinus (becomes large)

Tissue of the primitive gut tube...

Endoderm (derived via the yolk sac)

gut tube is suspended by

mesenteries (dorsal and ventral)

Where is the gut tube suspended

Splanchnic mesoderm

What forms mesenteries?

Splanchnic and somatic mesoderm
- Two layers of peritoneum

Parietal peritoneum derived from...

somatic mesoderm (mesentery peritoneum)

Visceral peritoneum derived from...

splanchnic mesoderm (mesentery peritoneum(

Foregut blood supply

Celiac trunk artery

Midgut blood supply

Superior mesenteric artery

Hindgut blood supply

Inferior mesentery artery

Foregut consists of...

Esophagus, stomach, liver, gallbladder, pancreas, spleen, proximal duodenum

Midgut consists of...

Distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal 2/3 of transverse colon

Hindgut consists of...

Distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, upper 2/3 of anal canal

Lesser omentum is a derivative of the ___________ mesentery and has attachments to the _________ curvature of the stomach

Ventral, lesser

Greater omentum is a derivative of the ___________ mesentery and has attachments to the _________ curvature of the stomach

Dorsal, greater

Prior to stomach rotation; spleen develops in the ________ mesentery and the liver develops in the __________ mesentery

Dorsal, ventral

Esophagus is lined with...

Endoderm

Stomach has 4 attachments to it. What are they?

Left & right vagus nerve, dorsal mesentery (attached to posterior wall), ventral mesentery (attached to anterior wall)

Stomach will dilate on the ______ side, and then will rotate ______ degrees

Left, 90