Head and Neck Anatomy: Introduction to Embryology and Dermatology

Flashcards covering the fundamentals of human embryology, including germ layer derivatives and early development, alongside an introduction to dermatology focusing on skin layers and appendages.

Zygote

A $2N$ cell formed on Day 1 after fertilization.

Morula

A structure produced by cleavage on Day 4 of early embryogenesis.

Blastula

A structure formed on Day 5 when a fluid-filled cavity develops inside the morula, eventually splitting into the embryoblast and trophoblast.

Gastrulation

The process where a 1-layer embryoblast becomes a 2-layer (bilaminar) then 3-layer (trilaminar) gastrula.

Epiblast

The dorsal layer of the bilaminar disc.

Hypoblast

The ventral layer of the bilaminar disc.

Primitive streak

A thickening down the midline of the epiblast during Week 3 that establishes the cranial-caudal axis.

Ectoderm

The germ layer that replaces the epiblast and gives rise to nervous tissue and epithelium.

Mesoderm

The germ layer that migrates ventrally between the epiblast and hypoblast, giving rise to muscle and connective tissue.

Endoderm

The germ layer that replaces the hypoblast and forms the epithelial lining of the gut tube and its derivatives.

Neurulation

A Week 3 process where the ectoderm folds and divides into the surface ectoderm, neural tube, and neural crest cells.

Surface Ectoderm

A derivative of ectoderm that forms the epidermis, nails, hair, oral epithelium, enamel of teeth, and the anterior pituitary.

Neural Tube

A derivative of ectoderm that forms the central nervous system, including the brain, spinal cord, and posterior pituitary.

Neural Crest Cells

Ectodermal derivatives that form sensory and autonomic neurons, melanocytes, dentin of teeth, and connective tissues of the head.

Notochord

A condensation of axial mesoderm that signals neural development and becomes the nucleus pulposus of the intervertebral disc in adults.

Somite

Segmented paraxial mesoderm that divides into the sclerotome, dermatome, syndetome, and myotome.

Sclerotome

The portion of a somite that becomes the vertebrae, ribs, and occipital bone.

Myotome

The portion of a somite that becomes skeletal muscle, including epimere (deep back muscles) and hypomere (hypaxial muscles).

Skin dermatome

An area of skin supplied by a sensory branch of a single spinal nerve.

Intermediate Mesoderm

The germ tissue that gives rise to the urinary system (kidneys, ureters, bladder) and the reproductive system.

Somatic Lateral Plate Mesoderm (SoLPM)

Mesoderm that forms connective tissues, bones (limbs, sternum, pelvis), and smooth muscle associated with the outer tube.

Splanchnic Lateral Plate Mesoderm (SpLPM)

Mesoderm that forms the heart, blood vessel endothelium, and smooth muscle associated with the visceral inner tube.

Branchial Arches

Also known as pharyngeal pouches, these give rise to the tissues of the face and neck.

Epidermis

The avascular outer layer of skin containing keratinocytes and melanocytes.

Dermis

The skin layer containing accessory and support structures such as hair follicles, glands, and neurovasculature.

Subcutis

Also known as superficial fascia, it consists of loose connective tissue and fat connecting skin to underlying structures.

Arrector pili muscle

Smooth muscle controlled by autonomic nerves that is associated with the hair follicle.

Herpes zoster (Shingles)

A condition caused by the Varicella zoster virus that produces skin rashes and blisters in a limited dermatome.