Comprehensive Guide to Epithelial and Connective Tissues in Human Anatomy

Histology

Study of tissues.

Epithelial tissue

Covers surfaces, lines passageways, forms glands.

Connective tissue

Fills spaces, provides support, stores energy.

Muscle tissue

Contracts for movement.

Neural tissue

Conducts electrical impulses, carries info.

Tissues

Collections of specialized cells + cell products that perform limited functions.

Organs

Multiple tissues working together → organ systems.

Characteristics of Epithelial Tissue

Tightly packed cells, apical surface exposed, attached to basement membrane, avascular, high regeneration rate.

Functions of Epithelial Tissue

Physical protection, control permeability, provide sensation, produce secretions.

Exocrine secretions

Secretions onto surfaces (sweat, enzymes, milk).

Endocrine secretions

Secretions into blood/tissue fluids (hormones).

Tight junctions

Seal; prevent water/solute passage.

Gap junctions

Connexons form channels for ions/small molecules (fast communication).

Desmosomes

Durable, tie cells together; resist stress.

Microvilli

Increase surface area for absorption/secretion.

Cilia

Movement of materials (e.g., respiratory tract).

Basement Membrane

Anchors epithelium to connective tissue; provides strength, barrier for large molecules.

Renewal/Repair of Epithelial Tissue

Short life span (1-2 days); replaced by stem cells near basement membrane.

Simple epithelium

Single layer; thin, fragile, absorption/secretion.

Stratified epithelium

Multiple layers; protection against stress.

Squamous epithelium

Thin, flat.

Cuboidal epithelium

Cube-like.

Columnar epithelium

Tall, slender.

Pseudostratified columnar epithelium

Appears layered; often ciliated; found in trachea, nasal cavity.

Transitional epithelium

Stretches/recoils; found in bladder, ureters.

Glandular Epithelium

Exocrine glands → ducts; mucous or serous; Endocrine glands → ductless; hormones.

Merocrine secretion

Exocytosis (saliva, sweat, mucus, milk).

Apocrine secretion

Cytoplasm + secretion lost (milk, viscous sweat).

Holocrine secretion

Cell bursts (sebaceous glands → oils).