Connective Tissue and Integumentary System: Study Guide

Chapter 4: Connective Tissue and Epithelial Tissue

Connective Tissue: Components and Types

Connective tissue is one of the four basic tissue types in the human body, providing support, binding, and protection for organs. It is characterized by its diverse cell types and abundant extracellular matrix.

• Three Components of Connective Tissue:

  • Cells: Various types including fibroblasts, adipocytes, macrophages, and others.

  • Fibers: Collagen, elastic, and reticular fibers provide strength, elasticity, and support.

  • Ground Substance: Amorphous material that fills the space between cells and fibers, composed of water, glycosaminoglycans, proteoglycans, and glycoproteins.

• Types of Fibers in Connective Tissue:

  • Collagen fibers: Strong, flexible, and resistant to stretching; most abundant.

  • Elastic fibers: Stretch and recoil, providing elasticity to tissues.

  • Reticular fibers: Thin, branching fibers that form supportive networks in soft tissues.

• Types of Connective Tissue:

  • Loose connective tissue: Areolar, adipose, and reticular tissues; found under epithelia and around organs.

  • Dense connective tissue: Dense regular, dense irregular, and elastic tissues; found in tendons, ligaments, and dermis.

  • Specialized connective tissue: Cartilage, bone, and blood.

• Difference Between Brown and White Fat:

  • White fat: Stores energy, insulates, and cushions organs.

  • Brown fat: Generates heat through non-shivering thermogenesis, especially in infants.

• Cells Found in Connective Tissue and Their Functions:

  • Fibroblasts: Produce fibers and ground substance.

  • Adipocytes: Store fat.

  • Macrophages: Phagocytize debris and pathogens.

  • Mast cells: Release histamine and play a role in inflammation.

  • Plasma cells: Produce antibodies.

• Reticular Connective Tissue:

  • Forms the stroma (supportive framework) of lymphoid organs such as lymph nodes, spleen, and bone marrow.

• Extracellular Matrix Components:

  • Composed of fibers (collagen, elastic, reticular) and ground substance (water, proteoglycans, glycoproteins).

Epithelial Tissue: Characteristics

• Characteristics of Epithelial Tissue:

  • Cells are closely packed with minimal extracellular matrix.

  • Arranged in continuous sheets (single or multiple layers).

  • Avascular (lacks blood vessels); receives nutrients by diffusion.

  • Has a high rate of cell division for renewal and repair.

  • Exhibits polarity (apical and basal surfaces).

• Main Anatomical Difference Between Bone and Cartilage:

  • Bone: Hard, mineralized matrix; contains blood vessels; supports and protects organs.

  • Cartilage: Firm but flexible matrix; avascular; provides support and cushioning in joints.

Chapter 5: The Integumentary System (Skin)

Skin Cancer and Risk Factors

• Greatest Risk Factor for Skin Cancer: According to most textbooks, exposure to ultraviolet (UV) radiation from the sun is the greatest risk factor.

• Rule of Nines: A method used to estimate the percentage of body surface area affected by burns. The body is divided into regions, each representing 9% (or multiples) of the total body surface area.

Glands of the Skin

• Mechanisms of Secretion:

  • Merocrine (eccrine) glands: Secrete via exocytosis (e.g., sweat glands).

  • Apocrine glands: Part of the cell's cytoplasm is released with the secretion (e.g., some sweat glands in axilla and groin).

  • Holocrine glands: Entire cell disintegrates to release its product (e.g., sebaceous glands).

• Types of Skin Glands and Their Secretions:

  • Sebaceous glands: Secrete sebum (oily substance) to lubricate skin and hair.

  • Sweat glands: Eccrine (watery sweat for thermoregulation) and apocrine (thicker secretion, associated with scent).

  • Ceruminous glands: Produce earwax (cerumen).

  • Mammary glands: Secrete milk.

Skin Anatomy and Function

• Layers of the Epidermis (from superficial to deep):

  1. Stratum corneum

  2. Stratum lucidum (only in thick skin)

  3. Stratum granulosum

  4. Stratum spinosum

  5. Stratum basale

• Vital Functions of Skin:

  • Protection from mechanical, chemical, and biological damage.

  • Prevention of water loss.

  • Thermoregulation.

  • Sensory reception.

  • Vitamin D synthesis.

  • Excretion of wastes through sweat.

Sensory Receptors and Dermis Anatomy

• Sensory Receptors in Skin:

  • Meissner's corpuscles: Light touch, located in dermal papillae.

  • Pacinian corpuscles: Deep pressure and vibration, located deeper in dermis/hypodermis.

  • Merkel cells: Touch receptors in the epidermis.

  • Free nerve endings: Pain and temperature.

• Layers of the Dermis:

  • Papillary layer: Superficial, areolar connective tissue, forms dermal papillae.

  • Reticular layer: Deeper, dense irregular connective tissue, provides strength and elasticity.

Specialized Cells and Burn Classification

• Langerhans Cell: A dendritic cell in the epidermis involved in immune response.

• Burn Classification:

  • First-degree burn: Affects only the epidermis; redness and pain.

  • Second-degree burn: Involves epidermis and part of dermis; blisters and pain.

  • Third-degree burn: Destroys epidermis and dermis; may extend into subcutaneous tissue; often painless due to nerve damage.

Endocrine vs. Exocrine Glands

• Endocrine Glands: Ductless glands that secrete hormones directly into the bloodstream (e.g., thyroid, pituitary).

• Exocrine Glands: Secrete products into ducts that open onto body surfaces or into body cavities (e.g., sweat, salivary, sebaceous glands).