Anatomy & Physiology Study Guide: Tissues, Integumentary System, and Skeletal System

Tissues (Chapter 4)

Overview of Tissue Types

Tissues are groups of similar cells that perform specific functions in the body. The four primary tissue types are epithelial, connective, muscle, and nervous tissues.

• Epithelial Tissue: Characterized by polarity (distinct apical and basal surfaces), tight junctions/desmosomes (cell connections), support by connective tissue, avascularity (lacking blood vessels), and high regenerative capacity.

• Connective Tissue: Provides support, binds tissues, stores energy, and offers protection. Contains cells, fibers, and ground substance (matrix).

• Muscle Tissue: Specialized for contraction and movement. Includes skeletal, cardiac, and smooth muscle types.

• Nervous Tissue: Specialized for communication via electrical impulses. Composed of neurons and supporting glial cells.

Epithelial Tissue

• Functions: Protection, absorption, filtration, excretion, secretion, and sensory reception.

• Types:

  • Simple Epithelium: Single cell layer (e.g., simple squamous, cuboidal, columnar).

  • Stratified Epithelium: Multiple layers (e.g., stratified squamous, cuboidal, columnar).

  • Specialized Types: Pseudostratified, transitional.

• Glands: Epithelial structures that secrete substances. Endocrine glands release hormones into the blood; exocrine glands secrete onto surfaces (e.g., sweat, oil glands).

• Membranes: Epithelial tissue forms body membranes:

  • Cutaneous: Skin (dry, protective)

  • Mucous: Lines open cavities (moist, secretes mucus)

  • Serous: Lines closed cavities (secretes serous fluid)

Connective Tissue

• Main Functions: Binding, support, protection, insulation, and transportation (blood).

• Components: Cells (fibroblasts, chondrocytes, osteocytes, etc.), fibers (collagen, elastic, reticular), and ground substance.

• Types:

  • Connective Tissue Proper: Loose (areolar, adipose, reticular) and dense (regular, irregular, elastic).

  • Cartilage: Hyaline, elastic, fibrocartilage.

  • Bone: Compact and spongy bone.

  • Blood: Fluid connective tissue.

Muscle and Nervous Tissue

• Muscle Tissue: Responsible for movement. Types include:

  • Skeletal Muscle: Voluntary, striated.

  • Cardiac Muscle: Involuntary, striated, found in the heart.

  • Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

• Nervous Tissue: Composed of neurons (transmit electrical signals) and neuroglia (supporting cells).

Integumentary System (Chapter 5)

Structure and Function

The integumentary system consists of the skin and its derivatives (hair, nails, glands). It serves as a protective barrier, regulates temperature, and provides sensory information.

• Skin Layers:

  • Epidermis: Keratinized stratified squamous epithelium. Main cell types: keratinocytes (produce keratin), melanocytes (produce melanin), dendritic (Langerhans) cells (immune defense), and tactile (Merkel) cells (sensory).

  • Dermis: Connective tissue layer beneath the epidermis. Contains blood vessels, nerves, glands, and hair follicles. Two layers: papillary (areolar connective tissue) and reticular (dense irregular connective tissue).

• Hypodermis (Subcutaneous Layer): Not part of the skin proper; consists mainly of adipose tissue for insulation and energy storage.

• Skin Appendages: Hair, nails, sweat glands (eccrine and apocrine), sebaceous (oil) glands.

• Functions: Protection, temperature regulation, sensation, metabolic functions (e.g., vitamin D synthesis), excretion.

Skeletal System (Chapter 6)

Structure and Function

The skeletal system provides support, protection, movement, mineral storage, blood cell formation, and energy storage.

• Cartilage: Types include hyaline (most common, found at joints), elastic (ear, epiglottis), and fibrocartilage (intervertebral discs, pubic symphysis).

• Bones: Classified by shape: long, short, flat, irregular.

• Bone Functions: Support, protection, movement, mineral storage (calcium, phosphate), blood cell formation (hematopoiesis), triglyceride storage, hormone production.

• Bone Structure:

  • Compact Bone: Dense outer layer; structural units called osteons (Haversian systems).

  • Spongy Bone: Internal network of trabeculae; contains red bone marrow.

• Bone Cells: Osteogenic cells (stem cells), osteoblasts (bone-forming), osteocytes (mature bone cells), osteoclasts (bone-resorbing).

• Ossification: Bone formation process. Endochondral ossification (bone replaces cartilage) and intramembranous ossification (bone develops from fibrous membrane).

• Hormonal Control: Parathyroid hormone (PTH), calcitonin, growth hormone, sex hormones.

Table: Comparison of Cartilage Types

Type	Main Locations	Key Features
Hyaline	Joints, nose, trachea, larynx, costal cartilage	Most abundant, provides support with flexibility
Elastic	External ear, epiglottis	Contains elastic fibers, maintains shape
Fibrocartilage	Intervertebral discs, pubic symphysis, menisci	Strongest, resists compression

Key Equations and Concepts

• Calcium Homeostasis: Blood calcium levels are regulated by hormones:

  • Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts.

  • Calcitonin decreases blood calcium by inhibiting osteoclasts.

• Bone Growth Equation:

$\text{Bone Growth Rate} = \text{Osteoblast Activity} - \text{Osteoclast Activity}$

Additional info:

• Glial cells in nervous tissue include astrocytes, oligodendrocytes, microglia, and ependymal cells (CNS); Schwann cells and satellite cells (PNS).

• Melanin is the primary pigment responsible for skin color; carotene and hemoglobin also contribute.

• Vitamin D synthesis in the skin is initiated by UV light exposure.