Animal Tissues: Epithelial Tissue

• Tissues are a group of cells with similar structure performing specific functions
• Animals possess four basic tissue types: epithelial, connective, muscular, and nervous

Epithelial Tissue

• It forms organ and cavity linings and coverings
• Functions include protection, absorption, secretion, and excretion
• Cells are tightly packed, leaving minimal intercellular space
• It rests on a non-cellular basement membrane
• It exists as simple (single layer) or stratified (multiple layers)
• Types include squamous, cuboidal, columnar, ciliated, and glandular

Squamous Epithelium

• It is composed of thin, flat cells
• Functions include diffusion and filtration
• Locations include blood vessel linings (endothelium) and lung air sacs (alveoli)

Cuboidal Epithelium

• Cube-shaped cells comprise it
• Functions include secretion and absorption
• Locations include kidney tubules and salivary glands

Columnar Epithelium

• Column-shaped cells comprise it
• Functions include secretion and absorption
• Locations include stomach and intestine linings

Ciliated Epithelium

• It consists of columnar or cuboidal cells featuring cilia
• It facilitates substance movement in one direction
• Locations include the respiratory tract and fallopian tubes

Glandular Epithelium

• This is specialized for secretion
• Forms unicellular (goblet cells) or multicellular glands
• Exocrine glands secrete onto epithelial surfaces via ducts
• Endocrine glands secrete hormones directly into the bloodstream

Stratified Epithelium

• It consists of multiple cell layers
• Primarily functions in protection from wear and tear
• Location example: skin as stratified squamous epithelium

Connective Tissue

• It connects, supports, and separates tissues and organs
• Cells are scattered within an extracellular matrix
• This matrix consists of ground substance and fibers
• Types include blood, bone, cartilage, ligaments, tendons, areolar, and adipose

Blood

• This is a fluid connective tissue
• Its matrix is plasma
• It contains red blood cells (RBCs, erythrocytes), white blood cells (WBCs, leukocytes), and platelets (thrombocytes)
• Functions include gas, nutrient, hormone, and waste transport, plus immune defense, and blood clotting

Bone

• A hard type of connective tissue
• Its matrix is composed of calcium phosphate and collagen fibers
• Bone cells (osteocytes) reside in lacunae
• Functions include support, protection, movement, mineral storage, and blood cell formation

Cartilage

• It is flexible connective tissue
• Its matrix is composed of chondrin
• Cartilage cells (chondrocytes) are located in lacunae
• Types include hyaline, elastic, and fibrocartilage

Hyaline Cartilage

• This is the most common cartilage type
• It is bluish-white and translucent
• Locations include long bone ends, the nose, and the trachea

Elastic Cartilage

• It contains elastic fibers
• It is flexible
• Locations include the ear pinna and epiglottis

Fibrocartilage

• It contains collagen fibers
• It is tough and strong
• Location: intervertebral discs.

Ligaments

• They connect bone to bone
• They are composed of dense regular connective tissue
• They exhibit high tensile strength

Tendons

• They connect muscle to bone
• They are composed of dense regular connective tissue
• They exhibit high tensile strength

Areolar Tissue

• This is loose connective tissue
• It contains fibroblasts, macrophages, and mast cells
• The matrix contains collagen and elastic fibers
• It functions in support and cushioning
• Locations include around organs and under the skin

Adipose Tissue

• It contains fat cells (adipocytes)
• Functions include energy storage, insulation, and cushioning
• Locations include under the skin and around organs

Muscular Tissue

• It is specialized for contraction and movement
• It contains muscle fibers (cells)
• Types include skeletal, smooth, and cardiac

Skeletal Muscle

• It exhibits a striated appearance
• It is under voluntary control
• It attaches to bones
• Its function is to move the skeleton

Smooth Muscle

• It is non-striated
• It is under involuntary control
• It is located in internal organ walls (e.g., stomach, intestine, blood vessels)
• It functions to move substances through internal organs

Cardiac Muscle

• It is striated
• It is under involuntary control
• It is located in the heart
• It functions to pump blood

Nervous Tissue

• It is specialized for communication and control
• It contains neurons (nerve cells) and neuroglia (supporting cells)

Neurons

• Function: transmits electrical signals (nerve impulses)
• Parts: cell body (soma), dendrites (receive signals), axon (transmits signals)

Neuroglia

• Neuroglia support, insulate, and protect neurons
• Examples include astrocytes, oligodendrocytes, microglia, and Schwann cells

Learn about animal tissues with a focus on epithelial tissue. This tissue type provides protection, absorption, secretion, and excretion. Explore squamous, cuboidal, and columnar epithelium.