Unit 1 Skin Notes

Homeostasis

The process of maintaining a consistent internal environment or range within the body.

Epithelia

A tissue type that forms protective layers, involved in secretion and absorption; classified as simple, stratified, or pseudostratified.

Exocrine glands

Glands that secrete substances outside the body or into cavities, e.g., sweat glands, sebaceous glands.

Endocrine glands

Glands that secrete hormones directly into the bloodstream.

Connective tissue

A type of tissue that supports, binds together, and protects tissues and organs of the body.

Tight junctions

Intercellular junctions that prevent paracellular diffusion and maintain cell polarity.

Gap junctions

Intercellular junctions that allow for direct communication between adjacent cells through the exchange of ions and small molecules.

Desmosomes

Intercellular junctions that act like snap-like connections, allowing some diffusion between cells.

Neurons

Nerve cells that transmit impulses throughout the body; cannot divide but can regenerate in peripheral regions if the cell body remains intact.

Tissue types

Epithelial, connective, muscular, and nervous.

Scarring

The healing process of tissue that can result in erythematous, hypertrophic, or atrophic changes.

Fibroblasts

Cells found in connective tissue that produce collagen and other fibers.

Hypertrophy

An increase in cell size resulting in an overall increase in an organ or tissue.

Atrophy

A decrease in cell size or number, leading to a reduction in tissue or organ size.

Keratinocytes

The primary cell type found in the epidermis, responsible for producing keratin.

Microfilaments

Components of the cytoskeleton that provide structural support and support microvilli in the cell.

Stratum corneum

The outermost layer of the epidermis, composed of dead keratinized cells that provide a barrier to infection and dehydration.

Stratum lucidum

A thin transparent layer found only in thick skin, situated between the stratum corneum and stratum granulosum.

Stratum granulosum

The layer of the epidermis where keratinocytes begin to die and accumulate keratohyalin granules, contributing to the water barrier.

Stratum spinosum

The layer of the epidermis where keratinocytes appear spine-like due to desmosome connections; involved in strength and flexibility.

Stratum basale

The deepest layer of the epidermis that contains proliferating keratinocytes, melanocytes, and Merkel cells; responsible for new cell generation.

Papillary layer

The uppermost layer of the dermis, consisting of areolar connective tissue and containing blood vessels, lymphatic vessels, and sensory neurons.

Reticular layer

The deeper and thicker layer of the dermis, made of dense irregular connective tissue that provides strength and elasticity to the skin.

Epidermis

The outermost layer of skin, composed of keratinized cells that provide a barrier to protect underlying tissues and prevent water loss.

Dermis

The thicker, middle layer of skin beneath the epidermis, containing connective tissue, blood vessels, and various structures such as hair follicles and glands.

Hypodermis

The innermost layer of skin, consisting of loose connective tissue and fat, which helps anchor the skin to underlying structures and provides insulation and cushioning.

Simple Squamous Epithelium

A single layer of flat cells that allows for easy diffusion and filtration, found in areas like the alveoli and capillaries.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells; involved in secretion and absorption, commonly found in glands and kidney tubules.

Simple Columnar Epithelium

A single layer of tall, column-like cells often with microvilli or cilia; primarily functions in absorption and secretion, found in the lining of the stomach and intestines.

Stratified Squamous Epithelium

Multiple layers of cells, with the top layer being flat; provides protection against abrasion, found in the skin and lining of the mouth.

Stratified Cuboidal Epithelium

Rare epithelium consisting of multiple layers of cube-shaped cells; provides protection and is usually found in some glandular tissues.

Stratified Columnar Epithelium

A rare type of epithelium with multiple layers of cells where the surface layer is columnar; found in the male urethra and some gland ducts.

Pseudostratified Columnar Epithelium

Appears to have multiple layers due to varying cell heights but is a single layer; often ciliated and involved in secretion and movement of mucus, found in the respiratory tract.

Transitional Epithelium

Specialized epithelium that can stretch and change shape, found in the urinary bladder.

Connective tissue

Type of tissue that provides primarily support, binding, and protection, as well as the ability to store energy, transport nutrients, and assist in immune responses. The most abundant and diverse tissue type.

Proper Connective Tissue

This group of connective tissues offers structural integration and functional support within the body, encompassing both loose and dense connective tissue types. Develops from fibroblasts.

Cartilage

A semi-rigid form of connective tissue that provides support and flexibility; types include hyaline, elastic, and fibrocartilage. Develops from chondroblasts. Lacks blood vessels and nerve endings.

Bone

A hard connective tissue that provides structural support and protection for the body; it is involved in mineral storage and blood cell production. Develops from osteoblasts.

Blood

A fluid connective tissue that transports nutrients, wastes, gases, and hormones throughout the body. Develops from hemopoetic stem cells.

Loose Connective Tissue

Connective tissue that provides support and elasticity; it allows for the movement of organs and has a variety of cells and fibers.

Areolar Connective Tissue

A loose connective tissue that provides support, elasticity, and a reservoir of water and salts for surrounding tissues; it contains a variety of cell types and fibers.

Adipose Tissue

A type of loose connective tissue that stores fat, provides insulation, and serves as an energy reserve.

Reticular Tissue

Connective tissue that forms a network of fibers, providing a supportive framework for organs such as the liver and lymph nodes.

Dense Connective Tissue

Connective tissue that provides strength and resistance to stretching; it includes tendons and ligaments.

Dense Regular Connective Tissue

A type of connective tissue that consists of closely packed collagen fibers arranged parallel to each other, providing high tensile strength; commonly found in tendons and ligaments.

Dense Irregular Connective Tissue

A type of connective tissue characterized by a dense network of collagen fibers arranged irregularly; provides strength and support in multiple directions, found in the dermis of the skin and organ capsules.

Elastic (Dense) Connective Tissue

A type of dense connective tissue that contains a high proportion of elastin fibers, allowing for greater flexibility and resilience, found in structures like the lungs and arteries.

Collagen fibers

Strong, thick fibers that provide tensile strength and support in connective tissues, found in nails and tendons.

Elastic fibers

Thin, elastic fibers that allow tissues to stretch and return to their original shape, found in the walls of arteries and lungs.

Reticular fibers

Fine, branched fibers that form a network to support soft tissues and organs, mainly found in lymph nodes and the liver.

Hyaline Cartilage

A smooth and glassy type of cartilage that provides support and flexibility; commonly found in the nose, trachea, and at the ends of long bones.

Elastic Cartilage

A type of cartilage rich in elastic fibers, allowing it to maintain shape while being flexible; found in structures like the ear and the epiglottis.

Fibrocartilage

A tough and dense type of cartilage that can withstand pressure and tension; found in intervertebral discs, the pubic symphysis, and menisci of the knee.

Ground Substance

The amorphous, gel-like material that fills the spaces between cells and fibers in connective tissue, providing support and facilitating the exchange of nutrients and waste.

Proteoglycans

Complex macromolecules made up of a central protein core and attached glycosaminoglycan (GAG) chains, predominantly found in the extracellular matrix; they are essential for maintaining tissue structure and influencing cellular functions.

Glycosaminoglycans (GAGs)

Long, linear polysaccharides formed from repeating disaccharide units, often sulfated; they are crucial for attracting water and contributing to the viscosity and elasticity of various tissues.

Laminin

glycoprotein that forms the basement membranes in almost all animal tissues, adhesive

Fibrillin

Adhesive that forms elastic fibers in connective tissue, providing strength and flexibility

Melanocytes

Cells located in the epidermis that produce melanin, the pigment that gives skin its color and offers protection from ultraviolet radiation.

Dendritic Cells

Specialized immune cells that capture, process, and present antigens to T cells, essential for activating and regulating immune responses.

Sebaceous Glands

Exocrine glands that secrete sebum (oil) into hair follicles, providing lubrication and waterproofing to the skin. Increase production after puberty, causing acne

Sweat Glands

Exocrine glands responsible for producing sweat; play a key role in thermoregulation and waste excretion.

Eccrine Sweat Glands

A type of sweat gland that is found all over the body, producing a watery secretion to help cool the body.

Apocrine Sweat Glands

A type of sweat gland located in specific areas (e.g., armpits, groin) that secretes a thicker, milky fluid rich in proteins, contributing to body odor. Ceruminous (earwax), mammary, and ciliary (eyelid) glands are modified versions.

Holocrine Secretion

A method of secretion seen in sebaceous glands where entire cells disintegrate to release their contents.

Merocrine Secretion

A method of secretion where glandular cells release their products via exocytosis without losing cellular material, typical of eccrine sweat glands.

Apocrine Secretion

A method of secretion in which a portion of the gland cell's cytoplasm is pinched off along with the secretory product, typical for apocrine sweat glands.

Ectoderm

The outermost layer of germ cells in the developing embryo that eventually forms structures like skin, hair, and the entire nervous system.

Mesoderm

The intermediate layer of germ cells in the embryo responsible for forming tissues such as muscles, bones, and the circulatory system.

Endoderm

The innermost layer of germ cells in the embryo that develops into the lining of the digestive tract, respiratory system, and various internal organs including the liver and pancreas.

Erythematous scars

Scars that appear red or pink due to increased blood flow to the area, often resulting from inflammation or healing processes in the skin.

Hair Papilla

A small, nipple-like structure of connective tissue at the base of the hair follicle that supplies nutrients to the growing hair.

Medulla (of Hair)

The central core of a hair strand, consisting of soft, keratinized cells; present in thick hair but may be absent in fine hair.

Hair Cortex

The thickest layer of the hair shaft made up of elongated, keratinized cells; responsible for the hair's strength, color, and texture.

Outer Root Sheath

The outer protective layer of the hair follicle, derived from the epithelium, which surrounds the inner structures of the hair follicle.

Inner Root Sheath

The layer of the hair follicle that surrounds the hair shaft, composed of three cellular layers; helps maintain the shape of the hair.

Fibrous Sheath

A protective layer surrounding the hair follicle, composed of connective tissue, which provides structural support and protection.