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

Tissues: Types, Structure, and Function

Definition and Overview

Tissues are groups of cells and their extracellular matrix that work together to perform specific functions. The extracellular matrix consists of protein fibers and ground substance, providing structural and biochemical support to surrounding cells.

• Four primary tissue types: Epithelial, Connective, Muscle, and Nervous tissues.

• Each tissue type originates from specific embryonic layers (ectoderm, mesoderm, endoderm).

Epithelial Tissue

• Characteristics: Closely packed cells, minimal extracellular matrix, avascular, high regenerative capacity, presence of cell junctions.

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

• Classification: Based on cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

• Structure-Function Relationship: The type and arrangement of epithelial cells relate to their function. For example, stratified squamous keratinized epithelium is found in the epidermis of the skin, providing protection against abrasion.

Example: Simple squamous epithelium in alveoli allows for efficient gas exchange due to its thinness.

Glands

• Endocrine glands: Ductless, secrete hormones directly into the bloodstream.

• Exocrine glands: Secrete products via ducts (e.g., sweat, saliva).

• Unicellular glands: Goblet cells (produce mucus).

• Multicellular glands: Composed of multiple cells, can be simple or compound in structure.

Connective Tissue

• Functions: Support, protection, binding, insulation, and transportation of substances.

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

• Classification: Loose connective tissue, dense connective tissue, cartilage, bone, blood.

• Structure-Function Relationship: The composition and organization of connective tissue determine its function. For example, blood is a fluid connective tissue specialized for transport.

Example: Cartilage provides flexible support in joints, while bone offers rigid support and protection.

Muscle Tissue

• Types: Skeletal (voluntary), cardiac (involuntary), smooth (involuntary).

• Functions: Movement, posture, heat production.

• Structure-Function Relationship: Skeletal muscle fibers are striated and multinucleated, allowing for powerful contractions.

Nervous Tissue

• Components: Neurons (transmit electrical signals) and glial cells (support and protect neurons).

• Functions: Communication, control, integration of body functions.

• Structure-Function Relationship: The unique structure of neurons (dendrites, axons) enables rapid signal transmission.

Membranes of the Body

• Types: Mucous, serous, cutaneous, synovial membranes.

• Structure: Typically consist of epithelial tissue and underlying connective tissue.

• Functions: Protection, secretion, absorption, lubrication.

Example: The cutaneous membrane (skin) protects underlying tissues from pathogens and dehydration.

Integumentary System

Structure and Functions of the Skin

• Layers: Epidermis (outer), dermis (middle), hypodermis (deepest).

• Functions: Protection, sensation, thermoregulation, vitamin D synthesis, excretion.

Epidermis

• Strata: Stratum basale, spinosum, granulosum, lucidum (only in thick skin), corneum.

• Cell types: Keratinocytes (produce keratin), melanocytes (produce melanin), dendritic cells (immune function), tactile cells (sensory).

• Structure-Function Relationship: The arrangement of strata provides a barrier and allows for regeneration.

Dermis

• Layers: Papillary (areolar connective tissue), reticular (dense irregular connective tissue).

• Functions: Provides strength, elasticity, and houses blood vessels, nerves, and appendages.

Hypodermis

• Composition: Adipose and areolar connective tissue.

• Functions: Insulation, energy storage, shock absorption.

Skin Appendages

• Hair: Composed of keratin, grows from follicles, provides protection and sensation.

• Nails: Made of hard keratin, protect fingertips.

• Glands: Sebaceous (oil), sudoriferous (sweat), and ceruminous (earwax) glands.

Skeletal System

Functions and Classification of Bones

• Functions: Support, protection, movement, mineral storage, blood cell formation (hematopoiesis), triglyceride storage.

• Classification: Long, short, flat, irregular, and sesamoid bones.

Bone Structure

• Gross Anatomy: Diaphysis (shaft), epiphyses (ends), metaphysis, medullary cavity, periosteum, endosteum.

• Microscopic Anatomy: Compact bone (osteons), spongy bone (trabeculae), bone cells (osteocytes, osteoblasts, osteoclasts).

Bone Formation and Remodeling

• Ossification: Intramembranous (flat bones) and endochondral (long bones) processes.

• Bone Growth: Interstitial (length) and appositional (width) growth.

• Remodeling: Continuous process involving bone resorption and deposition.

Physiology of Bone Tissue

• Mineralization: Deposition of calcium and phosphate.

• Hormonal Regulation: Parathyroid hormone (PTH) and calcitonin regulate blood calcium levels.

Key Equations:

• $\text{Ca}^{2+} \text{ homeostasis:} \quad \text{PTH} \uparrow \Rightarrow \text{bone resorption} \uparrow \Rightarrow [\text{Ca}^{2+}]_{\text{blood}} \uparrow$

• $\text{Calcitonin} \uparrow \Rightarrow \text{bone deposition} \uparrow \Rightarrow [\text{Ca}^{2+}]_{\text{blood}} \downarrow$

Axial and Appendicular Skeleton

Overview

• Axial skeleton: Skull, vertebral column, thoracic cage.

• Appendicular skeleton: Limbs and girdles (pectoral and pelvic).

• Functions: Protection of vital organs, support, movement.

• Bone markings help connect bones to other structures or allow passage for important vessels and nerves.

• Process: Any projection or bump (e.g., sticking out part of a bone).

• Foramen: A hole or opening for nerves and blood vessels.

• Fossa: A shallow depression.

• Crest: A prominent ridge.

• Condyle: A rounded articular area.

• Spine: A sharp, slender projection.

• Head: A rounded, expanded end of a bone

Vertebral Column

• Regions: Cervical, thoracic, lumbar, sacral, coccygeal.

• Curvatures: Primary (thoracic, sacral) and secondary (cervical, lumbar).

• Special Features: Atlas (C1), axis (C2), vertebral foramen, intervertebral discs.

Articulations (Joints)

Types and Classification

• Structural classification: Fibrous, cartilaginous, synovial joints.

• Functional classification: Synarthroses (immovable), amphiarthroses (slightly movable), diarthroses (freely movable).

Synovial Joints

• Characteristics: Articular cartilage, joint cavity, synovial fluid, articular capsule, ligaments.

• Types: Plane, hinge, pivot, condyloid, saddle, ball-and-socket.

• Structure-Function Relationship: The stability of a joint is inversely related to its range of movement. For example, the shoulder joint (ball-and-socket) has high mobility but lower stability compared to the hip joint.

Table: Comparison of Tissue Types

Tissue Type	Main Function	Key Features	Example Location
Epithelial	Protection, absorption, secretion	Cells tightly packed, avascular	Skin, lining of GI tract
Connective	Support, binding, transport	Cells + fibers + ground substance	Bone, blood, cartilage
Muscle	Movement	Contractile fibers	Skeletal muscles, heart
Nervous	Communication	Neurons and glial cells	Brain, spinal cord

Additional info: These notes are based on a study guide for an Anatomy & Physiology course, covering foundational concepts in tissue types, the integumentary system, skeletal system, and articulations. The structure-function relationship is a recurring theme, emphasizing how anatomical features determine physiological roles.