Microvilli

• Small projections on epithelial cells.

• Function: increase surface area for absorption, especially in the intestines.

Goblet Cells

• Specialized epithelial cells.

• Function: secrete mucus to protect and lubricate surfaces.

Exocrine Glands

• Secrete products through ducts to the surface of an organ or tissue.

Endocrine Glands

• Release hormones directly into the bloodstream without using ducts.

Composition of Glands

• Made up of epithelial tissue.

Avascularity

• Definition: lacking blood vessels.

Basement Membrane

• Function: supports epithelial tissue and anchors it to connective tissue.

Simple Epithelial Tissues

• Types and Functions:

  • Simple Squamous: facilitates diffusion.

  • Simple Cuboidal: involved in secretion.

  • Simple Columnar: involved in absorption.

Keratin

• A protein that strengthens and waterproofs skin and epithelial cells.

Stratified Epithelium

• Consists of multiple layers of cells that provide protection against abrasion.

• Example: Stratified squamous epithelium found in skin, mouth, and esophagus.

Transitional Epithelium

• Found in urinary bladder and ureters; allows stretching.

Pseudostratified Epithelium

• Found in respiratory tract, such as trachea.

Fibroblasts

• Function: produce fibers, such as collagen, in connective tissue.

Cell Junctions

• Structures that connect adjacent cells or to the extracellular matrix.

• Types:

  • Tight Junctions: prevent leakage between cells.

  • Gap Junctions: allow communication and molecule exchange.

  • Desmosomes: anchoring junctions for strong cell connection.

  • Hemidesmosomes: attach epithelial cells to the basement membrane.

Mast Cells

• Release histamine; involved in inflammation and allergic responses.

Plasma Cells

• A type of white blood cell that produces antibodies.

Acinar Gland

• An exocrine gland with a rounded, sac-like shape.

Types of Secretion

• Apocrine Secretion: releases product with part of the cell membrane.

• Holocrine Secretion: ruptures the entire cell to release secretions.

• Merocrine Secretion: products released via exocytosis without loss of cell parts.

Cell Suffix Meanings

• -blast: immature cell that builds/form tissue.

• -cyte: mature cell that maintains tissue.

• -clast: cell that breaks down tissue.

Matrix of Connective Tissue

• The structure can be:

  • Solid (bone)

  • Liquid (blood)

  • Semisolid (cartilage)

Embryonic Connective Tissue

• Earliest form found in the embryo.

Neuroglia

• Support cells in the nervous system that protect and nourish neurons.

Mesenchyme

• Embryonic connective tissue that gives rise to all connective tissues.

Hyaluronic Acid

• A molecule for lubricating joints and maintaining connective tissue hydration.

Functions of Adipose Tissue

• Energy storage.

• Insulation.

• Cushioning of organs.

Lacuna

• A small space in bone or cartilage housing a cell.

Haversian System

• Concentric bone layers surrounding a central canal for blood vessels.

Lamella

• Concentric rings of bone matrix in compact bone.

Connexons

• Protein channels forming gap junctions between cells.

Canaliculi

• Tiny channels in bone connecting lacunae to allow communication between bone cells.

Serous Membrane

• Thin membrane lining closed cavities that secretes serous fluid.

Intercalated Discs

• Specialized junctions between cardiac muscle cells for synchronized contractions.

Bursa

• Fluid-filled sac reducing friction between tissues, e.g., bone and tendon.

Tendon

• Connects muscle to bone.

Ligament

• Connects bone to bone; stabilizes joints.

Blood-Brain Barrier

• Selective barrier protecting the brain from harmful substances in the blood.

Function of Mast Cells

• Release histamine and other substances during inflammatory and allergic responses.