Lab Notes: Histology, Epithelial Tissue, and the Integumentary System

Epithelial tissues

Acts as a protective cover for body surfaces, involved in secretion and absorption.

Connective tissues

Provides support, binds other tissues, and stores energy.

Muscle tissues

Essential for movement, includes smooth muscle (involuntary), skeletal muscle (voluntary), and cardiac muscle (involuntary).

Nervous tissues

Comprised of excitable cells (neurons) and supportive cells (neuroglia) that communicate through electrical signals.

Secretion

Produces and releases substances such as enzymes and hormones.

Protection

Acts as a barrier to protect underlying tissues from injury and pathogens.

Absorption

Absorbs nutrients and substances in areas like the intestines.

Sensation

Contains sensory nerve endings that alert the body to stimuli.

Filtration

Involved in the selective permeability of substances, such as in renal tubules.

Squamous

Flat cells that facilitate diffusion and filtration.

Cuboidal

Cube-shaped cells typically involved in secretion and absorption.

Columnar

Tall column-like cells involved in absorption and secretion; often contain cilia or microvilli.

Simple Epithelia

Single cell layer; typically provides filtration and absorption, found lining organs.

Stratified Epithelia

Multiple cell layers that offer protection against abrasion, located in areas subject to friction.

Simple Squamous : Characteristics

Single layer of flat cells facilitating diffusion and filtration.

Simple Cuboidal : Characteristics

Single layer of cube-shaped cells with centrally located nucleus.

Simple Columnar : Characteristics

Single layer of columnar cells, which may have goblet cells that produce mucus.

Pseudostratified Columnar Characteristics

Appears stratified but is actually a single layer of cells with varying heights; all cells are attached to the basement membrane.

Stratified Squamous : Characteristics

Multiple layers of flat cells; keratinized cells on skin surface, non-keratinized in moist linings.

Stratified Cuboidal : Characteristics

Multiple layers of cube-shaped cells, usually two layers.

Stratified Columnar Characteristics

Multiple layers with cuboidal cells at the base and columnar cells at the top.

Transitional: Characteristics

Multiple layers that can stretch and relax, accommodating fluctuations in volume.

Exocrine Glands: Function

Glands that secrete substances onto the skin surface or into hollow organs through ducts

Exocrine Glands: Examples

Sweat glands release sweat; salivary glands release saliva during digestion.

endocrine glands

Glands that release hormones directly into the bloodstream,

Endocrine Glands: Examples

The pancreas secretes insulin; adrenal glands release cortisol during stress.

Epidermis: Structure

The outermost layer composed of keratinized stratified squamous epithelium, crucial for protection and waterproofing.

Dermis

The layer beneath the epidermis, rich in blood vessels, nerves, and connective tissue, contributing to skin elasticity and strength.

Hypodermis

The deepest layer mainly made of adipose tissue and loose connective tissue, providing insulation, energy storage, and cushioning.

Stratum Corneum

Outermost layer made of dead, flattened keratinized cells providing a tough barrier to environmental threats.

Stratum Granulosum

Contains keratinocytes filled with keratohyalin granules that begin keratinization, contributing to waterproofing.

Stratum Spinosum

Known for its spiny appearance due to desmosomal connections between keratinocytes, providing strength and flexibility.

Stratum Basale

Deepest layer where mitotically active stem cells divide and generate new keratinocytes, includes melanocytes and Merkel cells for sensation.

Stratum Lucidum

Thin translucent layer found only in thick skin (palms and soles), providing additional protection.

Keratinocytes

Predominant cell type producing keratin, essential for the skin's protective barrier against environmental damage.

Melanocytes

Responsible for producing melanin, which contributes to skin color and provides UV protection.

Langerhans Cells

Antigen-presenting cells that play a crucial role in the immune response of the skin.

Merkel Cells

Sensory cells transmitting touch sensations, associated with nerve endings.

Papillary Layer

Composed of loose connective tissue; contains dermal papillae that project into the epidermis, increasing surface area for exchange of gases and nutrients; contains tactile corpuscles for light touch.

Reticular Layer

Denser layer of irregular connective tissue; contains larger blood vessels, nerves, and deeper receptors, providing strength and elasticity to the skin.

Meissner’s Corpuscles

Sensitive to light touch and vibration, located in the papillary layer.

Pacinian Corpuscles

Sensitive to deep pressure and vibration, located in the reticular layer.

Free Nerve Endings

Responsible for sensing pain, temperature, itch, and tickle sensations; prevalent throughout the dermis and epidermis.

Simple columnar: ciliated location

lining of bronchi, uterine tubes, and part of uterus

Simple columnar: Non-Ciliated

lining of digestive tract, gall bladder, gland and excretory ducts

Pseudostratified columnar: ciliated

lining of the trachea, upper respiratory tract

Pseudostratified columnar: Non-ciliated

lining of the male reproductive ducts

Stratified squamous: Keratinized

Epidermis

Stratified squamous: Non-keratinized

lining of esophagus, lining of mouth lining of vagina, cornea

Simple squamous

lining of the renal glomeruli, lung alveoli, heart, circulatory vessels, lymphatic vessels

Simple squamous

permeable, allowing small molecules to pass through quickly, lining areas where gases diffuse passively

simple cuboidal

renal collecting tubule walls, small gland ducts, surface of the ovaries

simple cuboidal

found wherever secretion and absorption functions are needed within the body

simple columnar

secretes and absorbs substances into or out of the organs, some have cilia to increase surface area

pseudostratified columnar

protects the body from foreign particles, secretes mucus, and helps with absorption

stratified squamous

found in areas of the body that experience high mechanical stress and friction.

stratified cuboidal

sweat gland ducts, mammary gland duct, salivary gland ducts

stratified cuboidal

in ducts exposed to mechanical stress and secretion demands, protecting the walls of ducts

stratified columnar

male urethra, pharynx, glandular ducts

stratified columnar

found in areas requiring both protection and secretion

transitional

lining of the bladder, ureters, part of the urethra

transitional

lines organs subjected to distension and contraction