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Tissues Review Guide

Review Guide: Tissues

1. Four Tissues of the Human Body

  • Epithelial Tissue

  • Connective Tissue

  • Muscle Tissue

  • Nervous Tissue

2. Functions of Epithelial Tissue

  • Protection of underlying structures

  • Absorption of substances

  • Secretion of substances

  • Filtration

  • Sensation (as it contains sensory nerve endings)

3. Characteristics of Epithelial Tissue

  • Cellularity: Composed almost entirely of cells with minimal extracellular matrix.

  • Polarity: Epithelial cells have an apical surface (the top) and a basolateral surface (the bottom).

  • Attachment: Epithelial tissue is anchored to the underlying connective tissue via the basal lamina, a thin layer of ECM.

  • Avascularity: Lacks blood vessels and receives nutrients through diffusion from underlying tissues.

  • Regeneration: High capacity for cell division and regeneration.

4. Polarity in Epithelial Tissue

  • Definition: Polarity refers to the structural and functional differences between the apical and basolateral surfaces of epithelial cells.

  • Apical Surface: The free surface that faces the body exterior or an organ cavity; often has microvilli or cilia to increase surface area or aid in movement of substances.

  • Basolateral Surface: The lower surface that is attached to the underlying connective tissue; involved in attachment and transport of materials to the tissue below.

5. Specialized Structures in Epithelial Cells

  • Microvilli: Structures that increase surface area for absorption, commonly found in the intestinal lining.

  • Cilia: Structures that propel fluids across the epithelial surface, found in the respiratory tract (trachea).

6. Basal Lamina Regions

  • Lamina Lucida: The layer close to the epithelium; provides a barrier to larger molecules.

  • Lamina Densa: The thicker layer, composed mainly of collagen and glycoproteins, offering strength and filtration.

7. Intercellular Junctions

  • Tight Junctions: Prevent leakage between cells; found in intestinal epithelium.

  • Adherens Junctions: Anchor cells together; found in tissues where mechanical stress is present, such as the heart.

  • Desmosomes: Provide strength; found in skin and cardiac muscle cells.

  • Gap Junctions: Allow communication between cells; found in cardiac muscle to synchronize contractions.

8. Regenerative Cells in Epithelial Tissue

  • Location: Stem cells are located typically near the basal surface of epithelial cells.

  • Reason: Epithelial tissue frequently undergoes wear and tear, requiring a supply of regenerative cells to maintain the tissue integrity.

9. Classification of Epithelial Tissue

  • By Number of Layers: Simple (one layer) or Stratified (multiple layers).

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

10. Types of Epithelia

  • Simple Squamous Epithelium: Found in alveoli of lungs; allows diffusion.

  • Simple Cuboidal Epithelium: Found in kidney tubules; involved in secretion and absorption.

  • Simple Columnar Epithelium: Found in the digestive tract; aids in absorption.

  • Pseudostratified Columnar Epithelium: Found in the trachea; has cilia for moving mucus.

  • Stratified Squamous Epithelium: Found in the skin; provides protection.

  • Transitional Epithelium: Found in the urinary bladder; allows stretching.

11. Examples of Epithelia and their Functions

  • Simple Squamous: Alveoli; allows rapid gas exchange due to thinness.

  • Simple Cuboidal: In glands, controls secretion and absorption.

  • Columnar: In the intestines, enhances nutrient absorption and secretion of mucus.

  • Pseudostratified: Ciliated, traps debris and pathogens in the respiratory tract.

  • Stratified Squamous: In areas subject to friction (skin, oral cavity).

12. Endocrine vs. Exocrine Glands

  • Endocrine Glands: Secrete hormones directly into the bloodstream (e.g., thyroid gland).

  • Exocrine Glands: Secrete substances through ducts to the epithelial surface (e.g., sweat glands).

13. Modes of Secretion in Exocrine Glands

  • Merocrine: Secretion occurs via exocytosis without loss of cell integrity (e.g., salivary glands).

  • Apocrine: Secretion involves the loss of apical part of the cell (e.g., mammary glands).

  • Holocrine: Cells rupture and release their entire contents (e.g., sebaceous glands).

14. Functions of Connective Tissue

  • Support and structural framework for the body.

  • Binding together other tissues.

  • Storage of energy and nutrients.

  • Transport of substances (e.g., blood).

  • Immune defense.

15. Major Components of Connective Tissue

  • Cells: Fibroblasts, macrophages, mast cells, adipocytes, etc.

  • Fibers: Collagen fibers, elastic fibers, reticular fibers.

  • Extracellular Matrix: Composed of ground substance and fibers.

16. Cells of Connective Tissue

  • Fibroblasts: Secrete fibers and ground substance.

  • Adipocytes: Store fat.

  • Macrophages: Phagocytize debris and pathogens.

  • Mast Cells: Involved in inflammatory responses.

17. Main Components of Extracellular Matrix

  • Ground Substance: A gel-like substance that provides medium for exchange of substances; contains proteoglycans and glycoproteins.

  • Fibers: Include collagen (strength), elastin (elasticity), and reticular fibers (support).

18. Types of Extracellular Matrix Fibers

a. Most Common Fiber: Collagen fibers.
b. Returns to Original Length After Stretching: Elastic fibers.
c. Resists Force in Many Directions: Reticular fibers.
d. Forms Sheaths Around Organs: Collagen fibers.
e. Resists Force in One Direction: Dense collagen fibers.
f. Branched and Wavy: Elastic fibers.
g. Network of Interwoven Fibers: Reticular fibers.
h. Long, Straight, and Unbranched: Collagen fibers.
i. Contains Elastin: Elastic fibers.

19. Another Name for Bone Tissue

  • Osseous tissue.

20. Fibers in Bone

  • Type: Collagen fibers; provide tensile strength.

21. Major Ion in Osseous Tissue

  • Calcium (Ca²⁺) is the major ion found in osseous tissue.

22. Characteristics of the Three Types of Cartilage

  • Hyaline Cartilage: Provides smooth surfaces for joint movement, flexible, found in ribs.

  • Elastic Cartilage: More elastic fibers for flexibility, found in the outer ear.

  • Fibrocartilage: Contains a lot of collagen, resists compression, found in intervertebral discs.

23. Locations of Cartilage Types

  • Hyaline Cartilage: Found in embryonic skeleton, articular cartilages in joints for smooth movement.

  • Elastic Cartilage: Found in the ear to maintain shape and allow flexibility.

  • Fibrocartilage: Found in menisci of knees, absorbs shock due to its dense nature.

24. Connective Tissue Types Comparison

  • Dense Regular Connective Tissue: Parallel collagen fibers; found in tendons, withstands pulling forces.

  • Dense Irregular Connective Tissue: Collagen fibers arranged irregularly; found in the dermis, withstands tension in multiple directions.

  • Elastic Connective Tissue: Contains a high concentration of elastic fibers; found in large arteries, allows for stretching.

25. Attachments in Connective Tissues

  • Tendons: Attach muscle to bone.

  • Ligaments: Attach bone to bone.

26. Characteristics of Areolar Connective Tissue

  • Structure: Loose fibers; a mix of collagen and elastin; allows for movement and flexibility.

  • Function Relation: Allows for cushioning and connecting other tissues; provides a medium for nutrient and gas exchange.

27. Subcutaneous Tissue for Shots

  • Good Site for Injection: Because it is well vascularized and allows easy access to blood circulation.

28. Components of Areolar Connective Tissue Diagram

  • Labeling Components: Collagen fibers, elastic fibers, fibroblasts, ground substance.

29. Name for Fat Tissue

  • Adipose Tissue: Commonly known as fat.

30. Cells Containing Fat

  • Adipocytes: Specialized cells that store fat.

31. Functions of Adipose Tissue

  • Energy storage, insulation, cushioning of organs, and hormone production (e.g., leptin).

32. Major Function of Reticular Tissue

  • Provides a supportive framework for organs, especially lymphatic tissues.

33. Location of Reticular Tissue

  • Found in lymph nodes, spleen, and bone marrow for its supportive role.

34. Major Fluid Connective Tissue

  • Blood: Considered the primary fluid connective tissue.

35. Characteristics of Blood

  • Components: Red blood cells (erythrocytes), white blood cells (leukocytes), platelets, and plasma.

  • Function: Transportation of gases, nutrients, hormones, and waste.

36. Membrane Locations in Human Body

  • Mucous Membranes: Line body cavities exposed to the exterior; found in respiratory, digestive, and urinary tracts.

  • Visceral Pleura: Covers organs like lungs, allowing for smooth movement.

  • Parietal Pleura: Lines the thoracic cavity.

  • Visceral Peritoneum: Covers abdominal organs.

  • Parietal Peritoneum: Lines the abdominal cavity.

  • Visceral Pericardium: Covers the heart.

  • Parietal Pericardium: Lines the pericardial cavity.

37. Functions of Serosae

  • Provides a smooth, frictionless surface for organs; problems can include inflammation (serositis) or fluid accumulation.

38. Potential Space in Serosae

  • A potential space refers to an area that can expand under pathological conditions and is normally collapsed.

39. Muscle Tissue Comparison

  • Skeletal Muscle: Multinucleated, striated, voluntary, cannot divide, found attached to bones.

  • Cardiac Muscle: Single nucleus, striated with intercalated discs, involuntary, cannot divide, found in the heart.

  • Smooth Muscle: Single nucleus, non-striated, involuntary, can divide, found in walls of hollow organs.

40. Definition of Neurotransmitter

  • Chemical messengers used by neurons to communicate with each other or with muscles.

41. Direction of Axon Impulses

  • Direction: Carries impulses away from the cell body toward other neurons or effectors (muscles/glands).

42. Direction of Dendrite Impulses

  • Direction: Carries impulses toward the cell body.

43. Neurons vs. Neuroglia

  • Neurons: Conduct electrical impulses, the primary cells of the nervous system.

  • Neuroglia: Supportive cells that protect, support, and insulate neurons; they do not conduct impulses.

44. Sequence of Events After Tissue Injury

  • Injuries trigger inflammation, followed by regeneration or repair of tissues; the process includes the formation of granulation tissue, rebuilding the extracellular matrix, and restoring functional integrity.