Compartmentation: Cells and Tissues – Study Notes for Anatomy & Physiology

Compartmentation: Cells and Tissues

Organization of the Body: Body Cavities

The human body is organized into distinct cavities that house organs and provide protection and compartmentalization for physiological functions.

• Body Cavities: Spaces within the body that contain organs.

• Anterior (Ventral) Cavity: Includes the thoracic and abdominopelvic cavities.

• Posterior (Dorsal) Cavity: Contains the cranial and vertebral cavities (brain and spinal cord).

Example: The heart is located in the thoracic cavity; the brain in the cranial cavity.

Subdivisions of the Anterior Body Cavity

• Thoracic Cavity: Houses lungs and heart, divided by the diaphragm.

• Abdominopelvic Cavity: Below the diaphragm, contains digestive, urinary, and reproductive organs.

Additional info: The thoracic cavity is protected by the rib cage; the abdominopelvic cavity is less protected, making abdominal organs more vulnerable to trauma.

Serous Membranes

Body cavities are often lined by serous membranes, which reduce friction and protect organs.

• Serous Membrane: Double-layered membrane surrounding organs.

• Visceral Layer: "Inner layer" attached to the organ.

• Parietal Layer: "Outer layer" attached to the cavity wall.

• Serous Cavity: Potential space between the layers, filled with serous fluid.

• Serous Fluid: Lubricates membranes so organs can move easily.

Example: The pleura surrounds the lungs; the pericardium surrounds the heart.

Serous Membrane Locations

• Pleura: Thoracic cavity, surrounds lungs.

• Pericardium: Thoracic cavity, surrounds heart.

• Peritoneum: Abdominopelvic cavity, surrounds abdominal organs.

Layer	Organ/Structure
Visceral pleura	Lung
Parietal pericardium	Wall of the chest
Visceral peritoneum	Wall of the abdomen

Abdominopelvic Cavity Organization

• Abdominal Cavity: Space below the diaphragm, above the pelvis.

• Pelvic Cavity: Space below the abdominal cavity, bounded by the bones of the pelvis.

• Peritoneal Cavity: Space between abdominal organs and the abdominal wall, lined by peritoneum.

Organ	Abdominal Cavity	Pelvic Cavity	Peritoneal Cavity
Liver	✔		✔
Lungs
Large Intestine	✔	✔	✔
Kidneys	✔

Introduction to Eukaryotic Organelles

Animal vs. Plant Cells

Eukaryotic cells contain membrane-bound organelles that perform specialized functions.

• Animal Cell: Contains nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, etc.

• Plant Cell: Contains all animal cell organelles plus chloroplasts and a central vacuole.

Ribosomes

• Function: Synthesize proteins from amino acids.

• Location: Free in cytoplasm or attached to rough ER.

Endomembrane System & Protein Secretion

• Endomembrane System: Group of organelles involved in protein and lipid synthesis and transport.

• Includes: Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, cell membrane.

Organelle	Function
Nucleus	Stores DNA, controls cell activities
Rough ER	Protein synthesis
Smooth ER	Lipid synthesis
Golgi Apparatus	Modifies, sorts, and packages proteins
Lysosomes	Digestive enzymes

Lysosomes & Peroxisomes

• Lysosomes: Contain hydrolytic enzymes for intracellular digestion.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

Central Vacuole (Plant Cells)

• Function: Stores water, maintains turgor pressure, stores nutrients and waste products.

Mitochondria & Chloroplasts

Mitochondria

• Function: Site of cellular respiration, produces ATP.

• Structure: Double membrane, inner membrane forms cristae, contains its own DNA.

Equation: $\text{Cellular Respiration:} \quad \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

Chloroplasts (Plant Cells)

• Function: Site of photosynthesis, converts solar energy to chemical energy.

• Structure: Double membrane, thylakoid stacks (grana), contains its own DNA.

Equation: $\text{Photosynthesis:} \quad 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

Introduction to the Cytoskeleton

• Cytoskeleton: Network of protein filaments providing cell structure, movement, and transport.

• Main Components: Microfilaments (actin), intermediate filaments, microtubules.

Type	Function
Microfilaments	Cell movement, shape
Intermediate Filaments	Structural support
Microtubules	Organelle movement, cell division

Cell Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between cells.

Biological Membranes

Fluid Mosaic Model

• Biological Membrane: Composed of a phospholipid bilayer with embedded proteins and cholesterol.

• Functions: Selective permeability, cell signaling, protection.

Types of Membrane Proteins

• Integral Proteins: Span the membrane.

• Peripheral Proteins: Attached to the surface.

Function	Description
Recognition	Marks cell for identification
Anchorage	Cell cytoskeleton & ECM anchoring
Transport	Molecular transport across membrane
Enzymes	Catalyze processes

Organization of DNA in the Cell

• Genome: The complete set of DNA in a cell.

• Chromatin: DNA and associated proteins in non-dividing cells.

• Chromosomes: Highly condensed chromatin in dividing cells.

DNA Replication

• Produces identical chromatids: Each chromosome is copied before cell division.

Introduction to Tissues & Histology

Types of Tissues

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

• Connective Tissue: Supports, binds, and protects organs.

• Muscle Tissue: Contracts to allow movement.

• Nervous Tissue: Transmits electrical signals.

Extracellular Matrix (ECM)

• Definition: Non-cellular component that provides structural and biochemical support to cells.

Introduction to Epithelial Tissue

• Functions: Protection, transport, sensation, secretion.

• Characteristics: Polarity, tightly packed, anchored to basement membrane, avascular but innervated, highly regenerative.

Structural Naming of Epithelial Tissue

• Simple: Single layer of cells.

• Stratified: Multiple layers of cells.

• Cell Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

Type	Location	Function
Simple Squamous	Air sacs of lungs, lining of blood vessels	Diffusion, filtration
Simple Cuboidal	Kidney tubules, glands	Secretion, absorption
Simple Columnar	Digestive tract lining	Absorption, secretion
Pseudostratified Columnar	Trachea, upper respiratory tract	Secretion, movement of mucus

Characteristics of Epithelial Tissue

• Polarity: Apical and basal surfaces.

• Anchored to Basement Membrane: Provides support and attachment.

• Avascular but Innervated: No blood vessels, but has nerve supply.

• Highly Regenerative: Rapid cell division and repair.

Additional info: Tight junctions in the small intestine are crucial for selective absorption of nutrients.