Tissues, Integumentary System, and Skeletal System

1. Functions of Key Cells and Structures

This section covers the definitions and functions of various cells and structures found in connective, epithelial, and skeletal tissues.

• Elastin: A protein that provides elasticity to tissues, allowing them to resume shape after stretching or contracting.

• Chondroblasts: Cells that produce cartilage matrix.

• Ligaments: Connective tissue bands that connect bones to other bones, providing joint stability.

• Osteoclasts: Cells that break down bone tissue during bone remodeling.

• Collagen: The main structural protein in connective tissues, providing strength and support.

• Osteoblasts: Cells responsible for bone formation.

• Exocrine glands: Glands that secrete substances onto epithelial surfaces via ducts (e.g., sweat, salivary glands).

• Osteocytes: Mature bone cells that maintain bone tissue.

• Fibroblasts: Cells that synthesize extracellular matrix and collagen in connective tissue.

• Tendons: Connective tissue structures that attach muscles to bones.

• Endocrine glands: Glands that secrete hormones directly into the bloodstream.

• Chondrocytes: Mature cartilage cells that maintain cartilage matrix.

• Hemocytoblasts: Stem cells in bone marrow that give rise to all blood cells.

• Adipocytes: Fat cells that store energy in the form of lipids.

2. Exocrine Gland Classification

Exocrine glands are classified based on their structure and mode of secretion.

• Merocrine glands: Secrete products via exocytosis (e.g., sweat glands).

• Apocrine glands: Release part of the cell cytoplasm with the secretion (e.g., mammary glands).

• Holocrine glands: Entire cell disintegrates to release its product (e.g., sebaceous glands).

3. Epithelial Tissue Types and Locations

Epithelial tissues line body surfaces and cavities, with various types adapted for specific functions.

• Simple squamous: Single layer of flat cells; found in alveoli of lungs, lining of blood vessels.

• Ciliated pseudostratified columnar: Appears layered but all cells touch the basement membrane; found in respiratory tract.

• Stratified squamous: Multiple layers of flat cells; found in skin, mouth, esophagus.

• Simple columnar: Single layer of tall, column-like cells; found in digestive tract lining.

• Simple cuboidal: Single layer of cube-shaped cells; found in kidney tubules, glands.

4. Connective Tissues: Categories and Functions

Connective tissues support, bind, and protect other tissues and organs.

• Loose connective tissue: Provides support and flexibility (e.g., areolar tissue).

• Dense connective tissue: Provides strong connections (e.g., tendons, ligaments).

• Cartilage: Provides flexible support (e.g., hyaline, elastic, fibrocartilage).

• Bone: Provides rigid support and protection.

• Blood: Transports nutrients, gases, and wastes.

5. Muscle Tissue Types

Muscle tissues are specialized for contraction and movement.

• Skeletal muscle: Voluntary, striated muscle attached to bones; responsible for body movement.

• Smooth muscle: Involuntary, non-striated muscle found in walls of hollow organs (e.g., intestines, blood vessels).

• Cardiac muscle: Involuntary, striated muscle found only in the heart; responsible for pumping blood.

Distinguishing features: Skeletal muscle is multinucleated and voluntary; cardiac muscle has intercalated discs; smooth muscle lacks striations.

6. Integumentary System Overview

The integumentary system includes the skin and its derivatives, serving as a barrier and playing roles in sensation, thermoregulation, and vitamin D synthesis.

• Epidermis: Outermost layer, provides protection.

• Dermis: Middle layer, contains blood vessels, nerves, glands.

• Hypodermis: Subcutaneous layer, stores fat and anchors skin.

7. Melanin and Keratin

Melanin: Pigment produced by melanocytes, protects against UV radiation.

Keratin: Structural protein in skin, hair, and nails, providing strength and waterproofing.

8. Epidermis, Dermis, and Hypodermis: Structure and Function

• Epidermis: Stratified squamous epithelium; protects against pathogens and water loss.

• Dermis: Dense connective tissue; provides strength, elasticity, and houses sensory receptors.

• Hypodermis: Loose connective and adipose tissue; insulates and cushions the body.

9. Layers of the Epidermis (Superficial to Deep)

1. Stratum corneum

2. Stratum lucidum (only in thick skin)

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale

10. Components of the Epidermis, Dermis, and Hypodermis

• Epidermis: Keratinocytes, melanocytes, Langerhans' cells, Merkel cells.

• Dermis: Collagen fibers, elastic fibers, blood vessels, nerves, glands.

• Hypodermis: Adipocytes, larger blood vessels, connective tissue.

11. Skin Glands and Cells

Various glands and specialized cells are found in the skin, each with unique functions.

12. Skin Cancer Cells

• Basal cell carcinoma: Originates from basal cells in the epidermis.

• Squamous cell carcinoma: Originates from squamous cells.

• Melanoma: Originates from melanocytes; most dangerous form.

13. Bone Structure and Function

Key terms related to bone anatomy and physiology:

• Osteon: Structural unit of compact bone.

• Osteoid: Unmineralized bone matrix produced by osteoblasts.

• Extracellular Matrix: Non-cellular component providing structural support.

• Osteoblasts: Cells that synthesize new bone matrix.

14. Bone Anatomy Terms

15. Hormonal Regulation of Bone

• Calcitonin: Lowers blood calcium by inhibiting osteoclast activity and promoting calcium deposition in bones.

• Parathyroid hormone (PTH): Increases blood calcium by stimulating osteoclasts to break down bone and release calcium.

16. Bone Ossification

• Intramembranous ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of skull).

• Endochondral ossification: Bone forms by replacing hyaline cartilage (e.g., long bones).

17. Axial and Appendicular Skeleton

The human skeleton is divided into two main parts:

• Axial skeleton: Skull, vertebral column, and rib cage.

• Appendicular skeleton: Limbs and girdles (pectoral and pelvic girdles).

Additional info: For exam preparation, students should be able to identify, define, and describe the function and location of all listed structures, as well as understand the processes of bone formation and hormonal regulation.