Human Body: Levels of Organization

• The body has levels of structural organization, from simple to complex

Levels of organization

• Chemical: Atoms and molecules
• Cellular: Cells and their organelles
• Tissue: Groups of similar cells (epithelial, connective, muscle, nervous)
• Organ: Contains two or more types of tissues
• Organ System: Organs working together
• Organismal: All organ systems combined

Organ Systems and Functions

• Integumentary: Protects body, regulates temperature
• Skeletal: Supports, protects, stores minerals, blood cell formation
• Muscular: Movement, posture, heat production
• Nervous: Control system, responds to stimuli
• Endocrine: Hormone production, growth, reproduction
• Cardiovascular: Transports oxygen, nutrients, waste
• Lymphatic: Immunity, returns fluids to blood vessels
• Respiratory: Gas exchange (oxygen, carbon dioxide)
• Digestive: Breaks down food, absorbs nutrients
• Urinary: Eliminates waste, regulates water balance
• Reproductive: Produces offspring

Feedback Mechanisms

• Negative Feedback: Reduces original stimulus (e.g., body temperature regulation, blood glucose levels)
• Positive Feedback: Enhances stimulus (e.g., childbirth, blood clotting)

Homeostatic Imbalance and Disease

• Imbalances disrupt normal body functions, leading to disease (e.g., diabetes, dehydration, hypertension)

Anatomical Terminology

• Anatomy: Study of body structure
• Physiology: Study of body function
• Anatomical Position: Standing, facing forward, arms at sides, palms forward

Abdominopelvic Regions and Quadrants

• Quadrants: RUQ, LUQ, RLQ, LLQ
• Nine Regions: Right/left hypochondriac, epigastric, right/left lumbar, umbilical, right/left iliac, hypogastric

Cell Structure and Function

• Organelles: Nucleus, mitochondria, ribosomes, etc.

Epithelial Tissue Classification

• Types: Simple/stratified squamous, cuboidal, columnar; pseudostratified; transitional

Connective Tissue Classification

• Types: Loose, dense, cartilage, bone, blood

Nervous Tissue Characteristics

• Components: Neurons and neuroglia

Muscle Tissue Classification

• Skeletal: Voluntary movement
• Cardiac: Heart contractions
• Smooth: Involuntary movements in organs

Membranes Comparison

• Cutaneous: Skin
• Mucous: Lines cavities
• Serous: Lines internal organs

Tissue Repair Steps

• Inflammation
• Organization
• Regeneration or fibrosis

Tissue Changes Over a Lifetime

• Aging reduces elasticity and healing capacity

Skin Layers and Functions

• Epidermis: Protection
• Dermis: Sensation, blood supply

Homeostatic Responses to Integumentary Imbalances

• Example: Sweating, vasoconstriction

Cartilage Structure and Function

• Hyaline: Flexibility
• Elastic: Shape retention
• Fibrocartilage: Shock absorption

Bone Classification and Structure

• Shapes: Long, short, flat, irregular

Bone Growth, Remodeling, and Repair Flowchart

• Hematoma formation → fibrocartilaginous callus → bony callus → remodeling

Homeostatic Responses to Skeletal Imbalances

• Calcium regulation: Controlled by parathyroid hormone and calcitonin

Bone Growth

• Bone growth occurs through two primary processes: intramembranous ossification and endochondral ossification
• Intramembranous Ossification forms flat bones within mesenchymal tissue without a cartilage template
• Osteoblasts differentiate from mesenchymal cells & secrete bone matrix
• Osteocytes are mature osteoblasts embedded in the bone matrix, maintaining bone tissue
• Osteoblasts form ossification centers, secrete osteoid, which then mineralizes
• Osteoblasts become trapped, they differentiate into osteocytes
• Endochondral Ossification forms most bones by replacing hyaline cartilage with bone tissue
• Cartilage provides a template that bone cells replace
• Chondrocytes form cartilage model and signal ossification
• Osteoblasts replace cartilage with bone matrix
• Osteoclasts break down cartilage remnants and reshape bone
• Cartilage calcifies & is invaded by blood vessels
• Osteoblasts deposit bone tissue while osteoclasts remodel the developing bone

Bone Remodeling

• Bone remodeling is a continuous process where old bone tissue is replaced with new to adapt bone structure to mechanical stress & repair minor damages
• Osteoclasts break down old bone (bone resorption)
• Osteoblasts form new bone tissue (bone deposition)
• Osteocytes sense mechanical stress and signal bone remodeling
• Bones remodel according to the mechanical stresses they experience
• Weight-bearing exercises can strengthen bones by stimulating osteoblast activity (Wolff's Law)

Bone Repair

• Bone repair restores bone structure and function after a fracture
• Blood vessels break, causing a hematoma (blood clot) at the fracture site
• Blood cells initiate clot formation & inflammatory cells clear debris
• Soft callus forms from collagen and cartilage, stabilizing the fracture
• Fibroblasts produce collagen, while chondroblasts form cartilage
• Soft callus is replaced by a hard bony callus of spongy bone
• Osteoblasts create new bone matrix, converting soft callus into hard callus
• The bony callus is remodeled into compact bone and restored to its original shape
• Osteoclasts resorb excess bone; osteoblasts deposit new bone to form compact bone

Explore the structural organization of the human body. Learn about the various organ systems and their functions, from the integumentary to the reproductive system, and understand how they work together to maintain homeostasis.