Human Body Orientation, Cells, Tissues, and Integumentary System: ANP Study Guide

Human Body: An Orientation

Subdisciplines of Anatomy

Anatomy is the study of the structure of the human body. It is divided into several subdisciplines:

• Gross (macroscopic) anatomy: Study of structures visible to the naked eye.

• Microscopic anatomy: Includes cytology (study of cells) and histology (study of tissues).

• Developmental anatomy: Study of structural changes throughout life.

• Surface anatomy: Study of external features.

• Regional anatomy: Study of specific body regions.

• Systemic anatomy: Study of organ systems.

Structural Organization of the Human Body

The human body is organized hierarchically:

1. Chemical level: Atoms combine to form molecules.

2. Cellular level: Cells are the basic units of life.

3. Tissue level: Groups of similar cells perform specific functions.

4. Organ level: Organs are made of different tissues.

5. Organ system level: Groups of organs work together.

6. Organismal level: The complete living individual.

Main Body Systems

Each body system has specific functions and major organs:

• Integumentary: Protection; includes skin, hair, nails.

• Skeletal: Support and blood cell formation; bones.

• Muscular: Movement; muscles.

• Nervous: Fast control; brain, spinal cord, nerves.

• Endocrine: Hormonal control; glands.

• Cardiovascular: Transport; heart, blood vessels.

• Lymphatic: Immunity; lymph nodes, vessels.

• Respiratory: Gas exchange; lungs.

• Digestive: Nutrient breakdown; stomach, intestines.

• Urinary: Waste removal; kidneys.

• Reproductive: Reproduction; ovaries, testes.

Standard Anatomical Position

The standard anatomical position is used as a reference:

• Standing upright

• Feet flat

• Arms at sides

• Palms facing forward

• Head and eyes forward

Regional and Directional Terms

Regional terms identify specific locations; directional terms compare positions:

• Axillary: Armpit

• Thoracic/Pectoral: Chest

• Buccal: Cheek

• Sternal: Breastbone area

• Popliteal: Back of knee

Directional terms:

• Superior: Above

• Inferior: Below

• Anterior: Front

• Posterior: Back

• Medial: Toward midline

• Lateral: Away from midline

• Superficial: Toward surface

• Deep: Away from surface

Paired directional terms compare two structures (e.g., "the heart is medial to the lungs").

Body Planes

• Sagittal: Divides left/right

• Midsagittal: Equal halves

• Frontal (coronal): Divides front/back

• Transverse: Divides upper/lower

Tube-within-a-Tube Body Plan

• Inner tube: Digestive tract

• Outer tube: Body wall

• Space between: Body cavity

• All vertebrates share: Bilateral symmetry, dorsal nerve cord, ventral body cavity

Body Cavities

Cavity	Subdivisions
Dorsal	Cranial, Vertebral
Ventral	Thoracic, Abdominopelvic (Abdominal, Pelvic)

Serous Membranes

Serous membranes line closed ventral cavities, reducing friction and allowing organ movement.

• Parietal: Lines cavity wall

• Visceral: Covers organ

• Serous fluid: Lubricates between membranes

Abdominal Quadrants

Quadrant	Abbreviation
Right Upper	RUQ
Left Upper	LUQ
Right Lower	RLQ
Left Lower	LLQ

Microscopy

• Light microscopy: Uses visible light, lower magnification

• Electron microscopy: Uses electron beam, very high resolution

Cells: The Living Units

Primary Cell Functions

Cells perform essential functions for life:

• Metabolism: Chemical reactions for energy and growth

• Growth: Increase in size

• Reproduction: Cell division

• Movement: Locomotion or internal transport

• Communication: Signaling between cells

Main Cell Components

• Plasma membrane: Boundary, regulates entry/exit

• Cytoplasm: Contains organelles and cytosol

• Nucleus: Control center, contains DNA

Plasma Membrane Structure and Function

• Phospholipid bilayer: Hydrophilic heads face outward, hydrophobic tails inward

• Selectively permeable: Controls what enters/exits

• Integral proteins: Embedded in membrane, often transport or receptors

• Peripheral proteins: Attached to membrane surface, often signaling or support

• Functions: Protection, selective transport, communication, recognition

Membrane Transport Mechanisms

• Simple diffusion: Movement from high to low concentration

• Osmosis: Water movement across membrane

• Facilitated diffusion: Uses protein carriers

• Active transport: Requires ATP

• Endocytosis: Cell takes in material (phagocytosis for solids, pinocytosis for liquids)

• Exocytosis: Vesicles release contents outside cell

Cell Organelles

• Ribosomes: Protein synthesis

• Rough ER: Protein processing

• Smooth ER: Lipid synthesis, detoxification

• Golgi apparatus: Packages proteins

• Lysosomes: Digestion of waste

• Mitochondria: ATP production

• Peroxisomes: Detoxification

• Cytoskeleton: Structural support

• Centrosome: Microtubule organization

• Centrioles: Spindle fiber formation

Nucleus and DNA

• Nucleus: Control center, contains DNA

• Nucleolus: Makes ribosomes

• DNA: Double helix structure

• Chromatin: DNA + proteins

• Chromosomes: Condensed chromatin; humans have 46 (23 pairs)

Cell Cycle and Mitosis

The cell cycle consists of interphase and mitosis:

• Interphase: G1 (growth), S (DNA replication), G2 (preparation for mitosis)

• Checkpoints: G1 (size/DNA damage), G2/M (DNA fully replicated?)

• Mitosis: Prophase (chromosomes condense), Metaphase (align in middle), Anaphase (separate), Telophase (nuclei reform)

• Cytokinesis: Cytoplasm divides, forming two identical cells

Example: Skin cells undergo mitosis to replace lost cells.

Tissues

Definition and Types

Tissues are groups of similar cells performing a specific function. There are four main types:

1. Epithelial tissue

2. Connective tissue

3. Muscle tissue

4. Nervous tissue

Epithelial Tissue

• Functions: Protection, absorption, filtration, secretion

• Characteristics: Polarity, avascular, rapid regeneration, attached to basement membrane

• Classification:

  • Layers: Simple (one layer), Stratified (multiple layers)

  • Shape: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall)

• Glands: Endocrine (no ducts, hormones into blood), Exocrine (ducts)

• Goblet cells: Secrete mucus

• Cell junctions: Tight (seal), Desmosomes (anchor), Gap (communication)

• Basal lamina: Anchors epithelium

• Cilia vs Microvilli: Cilia move substances; microvilli increase surface area

Connective Tissue

• Functions: Support, protection, binding, transport

• Components: Cells, fibers (collagen, elastic, reticular), ground substance

• Origin: Mesenchyme (embryonic tissue)

• Main ECM-producing cells: Fibroblasts

• Ground substance: Gel-like material supporting cells

Type	Main Function
Areolar	Loose packing
Adipose	Fat storage
Dense regular	Tendons
Dense irregular	Dermis
Cartilage	Support
Bone	Rigid support
Blood	Transport

Muscle Tissue

• Skeletal: Striated, voluntary, attached to bones

• Smooth: No striations, in organs, involuntary

• Cardiac: Striated, heart only, involuntary

Nervous Tissue

• Neurons: Conduct impulses

• Neuroglia: Support neurons

Inflammation vs Immune Response

• Inflammation: Immediate, nonspecific response

• Immune response: Specific defense

Edema

Edema is fluid accumulation in tissues, bringing nutrients and immune cells.

Tissue Repair

• Regeneration: Replacement with same cells

• Fibrosis: Scar tissue formation

• Organization: Clot replaced with tissue

The Integumentary System (Skin)

Skin Layers

• Epidermis: Superficial layer

• Dermis: Middle layer

• Hypodermis: Deepest layer; adipose and areolar connective tissue

Skin Statistics

• ~7% of body weight

• 1–2 mm thick on average

Functions of Skin

• Protection

• Temperature regulation

• Sensation

• Vitamin D synthesis

• Excretion

Epidermal Cell Types

• Keratinocytes: Produce keratin

• Melanocytes: Produce melanin pigment

• Langerhans cells: Immune defense

• Merkel cells: Sensory receptors

Five Epidermal Layers (Deep to Superficial)

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum (thick skin only)

5. Stratum corneum

Dermis Layers

• Papillary: Areolar connective tissue

• Reticular: Dense irregular connective tissue

Dermal papillae: Increase surface area and grip.

Pigments

• Melanin: Brown-black pigment

• Carotene: Yellow-orange pigment

• Hemoglobin: Red pigment in blood

Nails

• Nail plate

• Nail bed

• Matrix

• Cuticle

• Made of keratin

Hair Structure

• Medulla: Central core

• Cortex: Surrounds medulla

• Cuticle: Outer layer

Glands

• Sebaceous glands: Secrete sebum (oil)

• Sweat glands: Eccrine (cooling), Apocrine (scent)

Burns

Degree	Layers Affected
1st degree	Epidermis
2nd degree	Partial dermis
3rd degree	Full thickness

Skin Cancer Types

• Basal cell carcinoma

• Squamous cell carcinoma

• Melanoma: Most dangerous