Lecture 2: Introduction to Embryology and Dermatology

Around what week(s) of embryonic development do the nervous and cardiovascular systems form?

Week 3

Around what week(s) of embryonic development do the upper and lower limbs form?

Weeks 3-4

Around what week(s) of embryonic development do the ears and eyes form?

Week 4

Around what week(s) of embryonic development do the palate and teeth form?

Week 6

Around what week(s) of embryonic development do the external genitalia form?

Week 7

What happens in week 1 of embryogenesis?

Day 1: The 2n zygote forms

Day 4: Cleavage produces a morula

Day 5: Fluid forms in the morula, producing a blastula

Day 6: The blastula splits into the embryoblast and trophoblast

Day 6: Implantation

The blastula splits into the embryoblast and trophoblast. Which of these cell masses is the inner mass?

The embryoblast

What happens in week 2 of embryogenesis?

Gastrulation, which is the process of the 1-layer embryoblast becoming a 2-layered bilaminar disc, and then a 3-layered gastrula.

What axis does the process of gastrulation establish?

The ventral/dorsal axis

The ventral layer of the gastrula is referred to as the ____.

Hypoblast

The dorsal layer of the gastrula is referred to as the ____.

Epiblast

What happens in week 3 of embryogenesis?

The primitive streak forms along the epiblast, leading epiblast cells to migrate through the streak and form the germ layers.

What axis does the formation of the primitive streak establish?

The cranial/caudal axis

The primitive node indicates the ____ end of the gastrula.

Cranial

The epiblast becomes the ____.

Ectoderm

The hypoblast becomes the ____.

Endoderm

Where is the mesoderm located?

Between the ectoderm and endoderm.

What is embryo folding?

A lateral folding processes where the flat trilaminar disc folds around it self to make an outer, somatic tube and an inner, visceral or splanchnic tube.

What are the three components of the ectoderm?

Non-neural ectoderm

Neuroectoderm

Neural plate border

Following neurulation, the non-neural ectoderm becomes the ____.

Surface ectoderm

Following neurulation, the neuroectoderm ectoderm becomes the ____.

Neural tube

Following neurulation, the neural plate border ectoderm becomes the ____.

Neural crest cells

Derivatives of the surface ectoderm are ____.

Integumentary tissues

Endocrine tissues (Anterior pituitary)

Oral tissues

Special sensory tissues

Derivatives of the neural tube are ____.

CNS (Brain, Spinal cord, Posterior pituitary)

PNS

Derivatives of the neural crest cells are ____.

PNS

Melanocytes

Dentin

Great vessels of heart

Connective tissues of head

Medulla of adrenal gland

The mesoderm is derived into the ____.

Axial mesoderm

Paraxial mesoderm

Intermediate mesoderm

Lateral plate mesoderm

The axial mesoderm becomes the ____. Its adult derivative is called the ____.

Notocord

Nucleus pulposus

Wrapped around the nucleus pulposus is the ____.

Annulus fibrosus

The paraxial mesoderm becomes ____.

Somites

Sclerotome somites make ____.

Vertebrae

Ribs

Occipital bone

Somite dermatome somites make ____.

The dermis over the spine (epaxial region)

Syndetome somites make ____.

Tendons

Myotome somites make ____.

Skeletal muscle

What does the term epimere refer to?

Epaxial, or deep back muscles

What does the term hypomere refer to?

Hypaxial muscles

What does the intermediate mesoderm become?

The urinary and reproductive systems

What does the lateral plate mesoderm become?

Somatic LPM (Connective tissues and outer tube smooth muscle)

Splanchnic LPM (Connective tissues and inner tube smooth muscle, blood vessels and heart tissues)

What does the endoderm become?

The oropharynx all the way through the respiratory system and gut

What are the branchial arches/pharyngeal pouches?

Visceral tissues that form the face and neck

They have a mesoderm and neural crest cell component

What are the layers of the skin?

Epidermis

Dermis

Subcutis (superficial fascia)

Where are apocrine sweat glands found?

Axial and groin region

Where are eccrine sweat glands found?

Everywhere

What is herpes zoster and what does it do?

Shingles

It causes the skin to blister and forms a rash in a limited skin dermatome.