64: Phylogeny and development of the skin Flashcards
(43 cards)
What is the origin of the epidermis?
Ectoderm.
What are the derivatives of the epidermis?
Feathers, hairs, and skin glands.
What are the characteristics of the epidermis?
Composed of keratinized, stratified squamous epithelium.
What is the origin of the dermis?
Mesoderm.
What are the characteristics of the dermis?
Made up of reticular connective tissue.
What is the origin of the hypodermis (tela subcutanea)?
Mesoderm.
What are the characteristics of the hypodermis?
Consists of reticular and adipose tissues.
What is keratin?
A fibrous structural protein forming the primary constituent of scales, nails, hooves, and horns in vertebrates.
What are corneous (horny) scales?
Found in reptiles like lizards and snakes; provide protection and assist in locomotion.
What are corneous (horny) plates?
Found in reptiles and some mammals, serving as armor.
What are feathers and their functions?
Exclusive to birds, crucial for flight, insulation, and display.
What are hairs (fur) and their functions?
Present in mammals, offering insulation, protection, and sensory functions.
What are placoid scales and where are they found?
Found in sharks, made of dentin covered by enamel, enhancing hydrodynamics and protection.
What are ganoid scales?
Present in certain ancient and living fishes, characterized by a rhombus shape and a hard enamel-like surface.
What are bony plates?
Dermal appendages that provide structural protection.
Define skin.
The soft, flexible outer tissue covering the body of vertebrate animals.
What are the functions of the skin?
- Protection: Shields against mechanical damage and pathogens.
- Hydration: Acts as a semi-impermeable barrier against excessive water loss.
- Thermoregulation: Provides insulation and regulates body temperature.
- Sensation: Contains nerve endings sensitive to various stimuli.
- Synthesis and Storage: Facilitates water retention, lipid synthesis, and production of Vitamin D.
- Respiratory Function: In some amphibians, serves as the primary respiratory organ.
What is the initial stage of epidermis development?
Starts as a single layer called the surface ectoderm.
What happens during periderm formation in epidermis development?
The surface ectoderm cells multiply and form the periderm, a temporary cover for the developing skin.
What occurs during stratification in the epidermis?
The epidermis starts layering, forming multiple layers of specialized cells.
What is cornification in epidermis development?
Cells at the outermost layer die, turning into a tough layer made of keratin and lipids, forming the protective barrier.
How does the permeability of fetal skin change during development?
Initially very permeable, it becomes impermeable post-cornification, sealing off the fetus from the surrounding fluid.
What are the key pathways in epidermal development?
- FGFs: Promote neural induction.
- BMPs and Wnt: Drive epidermal fate determination.
- Retinoic Acid and Sonic Hedgehog: Involved in epidermal cell fate decisions.
- Notch Signaling: Regulates the commitment between hair follicles and interfollicular epidermal lineages.
Describe the cellular hierarchy in epidermal development.
Stem cells (SCs) in the basal layer lead to committed progenitor cells (CPs), which further differentiate into terminally differentiated cells (TDs).
