Tissue. (copy)

Chapter 5: Tissues, Organs and Organ Systems

5.1 THE LEVELS OF ORGANIZATION

• Study of organisms shows increasing complexity.

• Cell organelles (e.g., nucleus, ribosomes, mitochondria) are specialized components of a cell.

• Organelle functions combine to form a single cell.

• Cells in multicellular organisms organize into tissues: groups of similar cells working together.

• Tissues form organs which are structures composed of two or more tissue types.

• Organ systems: groups of organs performing related functions.

• At every level, structure relates to function:

  • Example: Absorptive cells in small intestine differ from muscle cells.

  • Heart: Designed to pump blood; Lungs: Adapted for gas exchange.

Table 5.1: Levels of Organization

• Atomic Level: Smallest unit maintaining element properties (e.g., Carbon, Hydrogen, Oxygen).

• Molecular Level: Atoms form molecules with different properties (e.g., Water, DNA, Carbohydrates).

• Organelle Level: Biomolecules assemble into organelles (e.g., nucleus).

• Cellular Level: Basic unit of life (e.g., Muscle cell, Skin cell, Neuron).

• Tissue Level: Groups of similar cells (e.g., Muscle, Epithelial, Connective).

• Organ Level: Structures comprising different tissues (e.g., Heart, Liver, Stomach).

• Organ System Level: Groups of organs with related functions (e.g., Digestive System, Circulatory System).

• Organism Level: Entire living being with multiple organ systems (e.g., Human).

5.1.1 Organs

• Organs like the heart and lungs are composed of multiple tissue types designed for specific functions:

  • Heart: Pumps blood.

  • Lungs: Exchange gases (oxygen and carbon dioxide).

  • Skin: Protects internal structures.

• Most organs contain all four tissue types (Epithelial, Connective, Muscle, Nervous).

5.1.2 Organ Systems

• Organs are organized into systems that work together.

• Examples:

  • Cardiovascular System: Heart and blood vessels circulate blood.

  • Respiratory System: Facilitates gas exchange; includes nose, mouth, trachea, and lungs.

5.1.3 Cooperation of Organ Systems

• Organ systems work in tandem for homeostasis.

• Example: Respiratory and circulatory systems coordinate to deliver oxygen and remove carbon dioxide from cells.

5.2 HOMEOSTASIS

• Homeostasis: Maintenance of stable internal conditions (e.g., temperature, ion concentration).

• Critical for health; extreme variations can lead to illness.

5.2.1 Maintaining Homeostasis

• Biological systems adjust to maintain balance when disrupted (e.g., exercise raising body temperature).

5.2.2 Homeostatic Responses in Temperature Regulation

• Temperature regulation involves sensors relaying information to the hypothalamus in the brain.

• Responses to overheating include increased blood flow to skin and sweating to cool the body.

• A negative feedback mechanism is critical for temperature regulation.

5.3 MAJOR ORGAN SYSTEMS

• Table 5.2 summarizes organ systems and their homeostatic roles:

  • Cardiovascular: Transports nutrients and waste.

  • Lymphatic: Defends against diseases; maintains tissue fluid.

  • Digestive: Processes food; regulates nutrient levels.

  • Endocrine: Communicates within the body via hormones.

  • Integumentary: Protects against injury; fluid loss.

  • Muscular: Provides movement and heat.

  • Nervous: Processes information and maintains homeostasis.

  • Respiratory: Facilitates gas exchange.

  • Skeletal: Supports and protects; mineral storage.

  • Urinary: Removes waste and regulates water.

  • Immune: Defends against pathogens.

5.3 PLANT TISSUES

• Plants are multicellular and have differentiated tissues:

  • Composed of similar cells performing specific functions.

  • Tissues combine to form organs; each designed for particular tasks.

  • Three Main Types of Plant Tissues:

    • Dermal Tissue: Covers/protects the plant.

    • Ground Tissue: Site for photosynthesis, storage, and support.

    • Vascular Tissue: Transports water, minerals, and sugars.

5.3.1 Plant Organs and Organ Systems

• Plant organs like leaves, stems, and roots fulfill specific functions:

  • Leaves: Primary site for photosynthesis.

  • Stems: Support and transport substances.

  • Two Organs Systems:

    • Shoot System: Above ground parts.

    • Root System: Underground functions (anchoring, nutrient absorption).

5.3.2 Structure and Functions of Leaf Cells

• Leaves are thin, flat, and responsible for photosynthesis.

• Composed of various specialized cells:

  • Epidermis: Protects and prevents water loss; covered by a waxy cuticle.

  • Mesophyll: Two types:

    • Palisade Mesophyll: Contains chloroplasts for photosynthesis.

    • Spongy Mesophyll: Facilitates gas diffusion due to intercellular spaces.

  • Xylem: Transports water from roots.

  • Phloem: Carries produced food to other plant parts.