Tissue Types: Epithelial, Connective, Muscle & Nervous

• Four primary tissue types derive from three germ layers: Ectoderm, Mesoderm, and Endoderm.

Four Primary Tissue Types

• Epithelial Tissue is the lining, covering, and glandular tissue of the body.
• Glandular epithelium forms various glands.
• Connective Tissue connects body parts and is the most abundant and widely distributed tissue type.
• Muscle Tissue is highly specialized to contract and produce movement.
• Nervous Tissue receives and conducts electrochemical impulses; irritability and conductivity are its two major functions.

Epithelial Tissue

• Specialized tissue layers originate from the ectoderm, mesoderm, and endoderm.
• Classification is based on cell shape (squamous, cuboidal, columnar) and cell arrangement (simple, stratified).

Different Types of Lining/Covering Epithelium

• Simple Squamous Epithelium; Located in serous membranes, blood vessels, air sacs in the lungs (mesothelium).
• Simple Cuboidal Epithelium; Found in salivary glands, pancreas, walls of the kidneys, surface of ovaries.
• Simple Columnar Epithelium; Located in the digestive tract and contains goblet cells that produce lubricating mucus.
• Pseudostratified Columnar Epithelium; All cells rest on a basement membrane, but nuclei appear at different heights, giving a false impression of stratification.
• Pseudostratified Ciliated Columnar Epithelium; Ciliated variety that lines most of the respiratory tract.
• Stratified Squamous Epithelium; Exists in the mouth, esophagus, and outer portion of the skin (keratinized).
• Stratified Cuboidal Epithelium; Rare in the body. Found in ducts of large glands
• Transitional Epithelium; Seen in the urinary bladder, ureters, and urethra (Genitourinary tract).

Connective Tissue

• All connective tissues originate from embryonic mesenchyme, developing mainly from the mesoderm.
• Connective tissue supports organs and cells, acts as a medium for exchange of nutrients and wastes, protects against microorganisms, repairs damaged tissues, and stores fat.
• The main ingredient is collagen.

Different Connective Tissue Types

• Bone (osseous tissue); Composed of bone cells in cavities called lacunae, surrounded by a hard matrix containing calcium salts and collagen fibers.

• Cartilage; Is less hard and more flexible than bone.

• Hyaline Cartilage forms the supporting structures of the larynx, attaches the ribs to the breastbone, and covers the ends of bone where they form joints.

• Fibrocartilage forms the cushion-like discs between the vertebrae of the spinal column.

• Elastic Cartilage supports the external ear.

• Dense Connective Tissue forms tendons and ligaments

• Tendons attach skeletal muscles to bones

• Ligaments connect bones to bones at joints

• Loose Connective Tissue is softer with more cells and fewer fibers than other connective tissue types except blood.

• Areolar Tissue is the most widely distributed connective tissue.

• It functions as a universal connective tissue "glue".

• Adipose Tissue, commonly called fat, forms subcutaneous tissue, insulates the body, and protects it from extremes of heat and cold.

• Reticular Connective Tissue forms the stroma or internal framework in lymphoid organs like lymph nodes, the spleen, and bone marrow.

• Blood/Vascular Tissue acts as a transport vehicle for the cardiovascular system,.

Types of Muscle Tissue

• Skeletal Muscle is voluntary, striated, and has long, cylindrical, multinucleated cells with obvious striations.
• Cardiac Muscle is involuntary, striated, and has short, uninucleated, branching cells with intercalated disks.
• Smooth Muscle is involuntary, non-striated, and has uninucleated, spindle-shaped cells.
• It is found in the bladder, stomach, uterus, and blood vessels.

Nervous Tissue

• Nervous tissue contains nerve cells (neurons) that conduct electrical impulses.
• Supporting cells nurture and protect the neurons in the brain (glial/neuroglial cells in the CNS; satellite cells, capsule cells, and Schwann cells in the PNS).

Basic Parts of a Neuron

• Cell Body (Soma/Perikaryon); Contains the nucleus and surrounding cytoplasm, and is the primary trophic center.
• Dendrites receive signals and are principal signal reception and processing sites.
• Axon is wrapped in a myelin sheath and is the main conducting unit of a neuron.

Morphological Classification of Neurons

• Bipolar Neurons possess a single axon and a single dendrite (sense organs )
• Multipolar Neurons possess a single axon and more than one dendrite (most abundant/most common).
• Pseudounipolar Neurons possess a single process that branches into an axon and dendrite.

Overview of the four primary tissue types: epithelial, connective, muscle, and nervous tissue. Includes the origin of tissue layers (ectoderm, mesoderm, and endoderm) and classification based on cell shape and arrangement.