Anatomy & Physiology Study Guide: Tissue, Integumentary, and Skeletal Systems

Tissue Fundamentals

Concentration Gradients and Transport Mechanisms

Cells exchange substances with their environment through various mechanisms, governed by concentration gradients.

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP).

Example: Sodium-potassium pump in neurons uses active transport to maintain ion gradients.

Tissue Families and Their Characteristics

Tissues are groups of cells with similar structure and function. The four main types are:

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands.

• Connective Tissue: Supports, binds, and protects organs (e.g., bone, blood).

• Muscle Tissue: Responsible for movement (skeletal, cardiac, smooth).

• Nervous Tissue: Conducts electrical impulses, processes information.

Germ Layers: Endoderm, Mesoderm, Ectoderm

During embryonic development, three primary germ layers form:

• Endoderm: Forms internal linings (digestive, respiratory tracts).

• Mesoderm: Forms muscles, bones, connective tissue.

• Ectoderm: Forms skin and nervous system.

Tissue Repair

Tissue repair involves inflammation and regeneration.

• Inflammation: Mast cells release histamine, increasing blood flow and immune response.

• Regeneration: Replacement of damaged cells with new cells.

Nervous System Organization

Afferent vs. Efferent Pathways

The nervous system transmits information via two main pathways:

• Afferent (Sensory): Carries signals from receptors to the central nervous system (CNS).

• Efferent (Motor): Carries signals from CNS to effectors (muscles, glands).

Flowchart: Ascending (sensory) vs. Descending (motor) pathways.

Receptors and Effectors

• Receptors: Detect stimuli (e.g., thermoreceptors, mechanoreceptors).

• Effectors: Respond to signals (e.g., muscle contraction, gland secretion).

Integumentary System

Functions of the Integumentary System

The integumentary system protects the body and regulates its environment.

• Protection against pathogens and physical injury

• Regulation of body temperature

• Sensation (touch, pain, temperature)

• Excretion of wastes

• Synthesis of vitamin D

Cells of the Epidermis

• Keratinocytes: Produce keratin, provide waterproofing.

• Melanocytes: Produce melanin, protect against UV radiation.

• Langerhans Cells: Immune defense.

• Merkel Cells: Sensory receptors for touch.

Layers of Cutaneous Membrane and Epidermis

• Stratum Corneum: Outermost, dead keratinized cells.

• Stratum Lucidum: Only in thick skin (palms, soles).

• Stratum Granulosum: Keratin formation begins.

• Stratum Spinosum: Provides strength and flexibility.

• Stratum Basale: Deepest, mitotically active layer.

Glands: Modes of Secretion

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

• Apocrine Glands: Secrete by pinching off part of the cell (e.g., axillary sweat glands).

• Holocrine Glands: Secrete by cell rupture (e.g., sebaceous glands).

Dermis Layers

• Papillary Layer: Superficial, contains capillaries and sensory neurons.

• Reticular Layer: Deep, dense irregular connective tissue, provides strength.

Receptors in Integument

• Thermoreceptors: Monitor temperature changes.

• Nociceptors: Monitor pain (damage or potential damage).

• Proprioceptors: Monitor body position and movement.

• Mechanoreceptors: Monitor touch, pressure, vibration.

Skeletal System

Function of Bone

Bones provide structure, protection, and facilitate movement.

• Support for body tissues

• Protection of vital organs

• Leverage for movement

• Mineral storage (calcium, phosphate)

• Blood cell production (hematopoiesis)

Repair of Fractures

• Hematoma Formation: Blood clot forms at fracture site.

• Fibrocartilaginous Callus Formation: Collagen and cartilage stabilize the break.

• Bony Callus Formation: Osteoblasts produce new bone.

• Bone Remodeling: Bone is reshaped to original form.

Curvatures of the Vertebral Column

• Primary Curvatures: Thoracic and sacral, present at birth.

• Secondary Curvatures: Cervical and lumbar, develop after birth.

• Pathological Curvatures: Scoliosis (lateral), kyphosis (excessive thoracic), lordosis (excessive lumbar).

Cellular Components of Bone Tissue

• Osteoblasts: Build new bone matrix.

• Osteocytes: Mature bone cells, maintain bone tissue.

• Osteoprogenitor Cells: Stem cells that differentiate into osteoblasts.

• Osteoclasts: Break down bone matrix for remodeling and calcium release.

Endochondral vs. Intramembranous Ossification

• Endochondral Ossification: Bone develops from hyaline cartilage (most bones).

• Intramembranous Ossification: Bone develops directly from mesenchymal tissue (flat bones of skull).

Calcium Homeostasis

Calcium levels are regulated by the skeletal, digestive, and urinary systems.

• Skeletal System: Stores and releases calcium as needed.

• Digestive System: Absorbs calcium from food.

• Urinary System: Excretes excess calcium.

Key Equation:

$\text{Blood Calcium Level} = \text{Calcium Intake} - \text{Calcium Excretion} + \text{Calcium Released from Bone}$

Summary Table: Bone Cell Functions

Cell Type	Main Function
Osteoblast	Bone formation
Osteocyte	Maintenance of bone tissue
Osteoprogenitor Cell	Stem cell for osteoblasts
Osteoclast	Bone resorption

Additional info: Academic context and definitions have been expanded for clarity and completeness.