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Epithelial Tissue (ET)

Types of Simple Epithelial Tissue

Simple Squamous ET

Location:

  • Lung alveoli

  • Bowman’s capsule of renal corpuscle in the kidney (Filtration)

  • Glomerulus of renal corpuscle in the kidney (Diffusion)

  • Endothelium (Lines blood vessels to provide a smooth surface, reducing friction and facilitating blood flow)

  • Mesothelium (Covers organs, provides support and protection against friction)

  • Capillaries (Facilitates the rapid diffusion of gases, nutrients, and waste)

Function:

  • Diffusion of gases (Oxygen and carbon dioxide exchange)

Simple Cuboidal ET

Location:

  • Kidney tubules

  • Ducts of salivary glands

  • Ducts of pancreas

  • Follicles of the thyroid gland

Function:

  • Selective reabsorption (Regulation of substances such as electrolytes and water)

  • Hormone production (e.g., Thyroxine (T3, T4), Calcitonin, Parathyroid Hormone)

Simple Columnar ET

Location:

  • Lining of the digestive tract

  • Mucosa lining of the villi in the small intestine

  • Goblet cells in the digestive tract (Mucus-secreting cells)

Function:

  • Absorption of nutrients (Facilitated by microvilli enhancing surface area)

  • Secretion of mucin, forming mucus (Protects and lubricates the lining)

Types of Stratified Epithelial Tissue

Keratinized Stratified Squamous ET

Location:

  • Epidermis of the skin (Protects from environmental damage)

Function:

  • Provides strength and waterproofing (Keratinization prevents water loss)

Non-keratinized Stratified Squamous ET

Location:

  • Oral cavity, nasal cavity, pharynx, esophagus, vagina, anal canal

Function:

  • Protection against abrasion and moisture maintenance (Facilitates lubrication and protection)

Stratified Cuboidal ET

Location:

  • Ducts of sweat glands and mammary glands

Function:

  • Provides structural support (Contributes to the integrity of glandular structures)

Stratified Columnar ET

Location:

  • Parts of epiglottis, pharynx, anus, urethra, excretory ducts

Function:

  • Protection (Serves as a barrier against pathogens)

Simple Ciliated Columnar ET

Location:

  • Lines uterine tubes (fallopian tubes)

Function:

  • Transport material through the lumen (Cilia help move the egg toward the uterus)

Pseudostratified Ciliated Columnar ET

Location:

  • Trachea and bronchi (part of the respiratory system)

Function:

  • Remove foreign material and bacteria from the lower respiratory tract (Cilia and mucus trap and expel debris)

Transitional ET

Location:

  • Lines ureters and urinary bladder

Function:

  • Distension (Allows stretching to accommodate urine volume)

Glandular ET

Location:

  • Islets of Langerhans (pancreas, endocrine system)

  • Pancreatic acinar cells (digestive system, exocrine)

Function:

  • Secretion of hormones (e.g., glucagon, insulin)

  • Secretion of pancreatic enzymes (Essential for digestion)

Connective Tissue (CT)

Types of Connective Tissue

Loose (Areolar) CT

Location:

  • Surrounds blood vessels and nerves

  • Binds skin to muscles (superficial fascia)

  • Surrounds muscles (deep fascia), papillary region of dermis

Function:

  • Allows for flexibility and diffusion (Fluid matrix facilitates transport of nutrients and waste)

Dense Irregular CT

Location:

  • Reticular region of the dermis, fibrous capsules of organs and joints, periosteum of bone

Function:

  • Provides structural support and strength (Resists forces from multiple directions)

Dense Regular CT

Location:

  • Tendons and ligaments

Function:

  • Provides tensile strength (Resists pulling forces in one direction)

Elastic CT

Location:

  • Walls of large arteries, lower respiratory tract

Function:

  • Provides elasticity and extensibility (Allows structures to return to their original shape)

Reticular CT

Location:

  • Liver, spleen, lymph nodes, thymus, bone marrow

Function:

  • Provides structural support (Forms a scaffold for organs)

Adipose CT

Location:

  • Hypodermis, around kidneys, joints, heart, omentum, back of the eye

Function:

  • Provides protection, padding, energy storage (Insulation and shock absorption)

Bone CT

Location:

  • Compact and spongy bone

Function:

  • Provides structural support, hemopoiesis (Blood cell production in the marrow)

Hyaline Cartilage CT

Location:

  • Articular surfaces of bones, trachea, upper respiratory tract, nasal septum, costal cartilage, fetal skeleton

Function:

  • Provides support and flexibility (Cushions and supports structures)

Types of Cartilage

Elastic Cartilage CT

Location:

  • External ear, epiglottis, larynx, auditory canal

Function:

  • Provides flexibility (Allows for shape retention under stress)

Fibrocartilage CT

Location:

  • Menisci of the knee, intervertebral joints, pubic symphysis

Function:

  • Provides support and compression (Distributes weight and absorbs shock)

Cellular Components of Connective Tissue (CT)

  • Fibroblast: Produces collagen and elastic fibers.

  • Reticulocyte/Reticuloblast: Produces reticular fibers relevant for structure.

  • Chondrocyte: A specialized cartilage cell that maintains cartilage.

  • Osteocyte: A mature bone cell involved in maintaining bone tissue.

  • Adipocyte: A fat cell involved in energy storage.

  • Mast Cell: Involved in inflammation; produces heparin and histamine.

  • Monocyte: A phagocytic white blood cell (WBC) in the vasculature.

  • Macrophage: A mature monocyte that resides in tissues; involved in phagocytosis.

  • Plasma Cell: Produces antibodies crucial for immune response.

  • Erythrocyte: Transport oxygen and carbon dioxide.

  • Leukocyte: Involved in immune response.

  • Platelet: A cell fragment important in blood clotting.

Fibers of Connective Tissue (CT)

  • Collagen: Provides strength and support; the most abundant protein in the body.

  • Elastic Fibers: Allow connectivity and elasticity, contributing to the resilience of various tissues.

  • Reticular fibers: Provide a mesh-like structure for supporting cells and blood vessels.