Study Guide: Tissues, Integumentary System, and Skeletal System

Tissues

Definition and Classification

Tissues are groups of similar cells that perform a specific function. In the human body, there are four basic types of tissues, each with unique structures and functions.

• Cell Junctions: Specialized connections between cells that allow communication and adhesion. Types include tight junctions, desmosomes, gap junctions, and adherens junctions.

• Four Basic Types of Tissues:

  • Epithelial Tissue: Covers body surfaces and lines cavities. Functions include protection, absorption, secretion, and sensation.

    • Simple Squamous: Single layer of flat cells; found in alveoli and blood vessels; allows diffusion and filtration.

    • Simple Cuboidal: Single layer of cube-shaped cells; found in kidney tubules and glands; involved in secretion and absorption.

    • Simple Columnar (Ciliated & Non-ciliated): Single layer of tall cells; ciliated type lines respiratory tract, non-ciliated lines digestive tract.

    • Pseudostratified Columnar (Ciliated): Appears layered but is a single layer; ciliated type lines trachea.

    • Stratified Squamous (Keratinized & Non-keratinized): Multiple layers; keratinized forms skin, non-keratinized lines mouth and esophagus.

    • Stratified Cuboidal: Two or more layers of cube-shaped cells; found in sweat glands.

    • Stratified Columnar: Rare; found in male urethra.

    • Transitional: Specialized for stretching; lines urinary bladder.

    • Glandular Epithelium: Forms glands (endocrine and exocrine). Endocrine glands secrete hormones into the bloodstream. Exocrine glands secrete substances onto epithelial surfaces via ducts.

    • Structural & Functional Classification of Exocrine Glands: Classified by structure (unicellular/multicellular) and mode of secretion (merocrine, apocrine, holocrine).

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

    • Loose Connective Tissue: Includes areolar, adipose, and reticular tissues.

    • Dense Connective Tissue: Regular (tendons, ligaments), irregular (dermis), and elastic types.

    • Cartilage: Hyaline (ends of bones), fibrocartilage (intervertebral discs), elastic (ear).

  • Other Tissues:

    • Bone Tissue: Rigid support and protection.

    • Blood: Fluid tissue for transport of gases, nutrients, and waste.

    • Muscle Tissue: Skeletal (voluntary movement), cardiac (heart), smooth (walls of organs).

    • Nervous Tissue: Neurons and supporting cells; responsible for communication and control.

• Membrane Types: Epithelial and connective tissue membranes (e.g., mucous, serous, cutaneous, synovial).

• Tissue Repair: Process by which damaged tissues are replaced or healed.

Integumentary System

Major Components and Functions

The integumentary system consists of the skin and its derivatives. It serves as a barrier, regulates temperature, and provides sensory information.

• Skin Arrangement: Layers of the skin include the epidermis and dermis.

• Epidermis:

  • Composed of 4-5 cell layers (strata) depending on thickness.

  • Strata: Basale, spinosum, granulosum, lucidum (only in thick skin), corneum.

• Dermis:

  • Papillary Layer: Superficial, contains capillaries and sensory neurons.

  • Reticular Layer: Deeper, dense irregular connective tissue.

• Glands of the Skin:

  • Sebaceous Glands: Secrete sebum (oil).

  • Sweat Glands: Eccrine (thermoregulation), apocrine (armpits, groin).

  • Ceruminous Glands: Produce earwax.

• Hair: Structure, function, and growth cycle.

• Functions of the Skin: Protection, sensation, thermoregulation, excretion, vitamin D synthesis.

• Wound Healing: Involves inflammation, proliferation, and remodeling phases.

• Clinical Applications: Burns, skin cancers, and other disorders.

Skeletal System

Components and Classification

The skeletal system provides support, protection, and movement. It consists of bones, cartilage, and joints.

• Bone Classification: Based on shape (long, short, flat, irregular, sesamoid).

• Functions of the Skeleton: Support, protection, movement, mineral storage, blood cell production.

• Gross Anatomy of Bones: Structure includes diaphysis, epiphyses, medullary cavity, periosteum, endosteum.

• Types of Bone: Compact (dense) and spongy (cancellous).

• Histology of Bone: Osteons in compact bone; trabeculae in spongy bone.

Bone Formation and Growth

• Intramembranous Ossification: Bone develops from fibrous membrane (e.g., flat bones of skull).

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

• Growth: Interstitial (length) and appositional (width) growth; occurs at epiphyseal plate.

Bone Remodeling and Homeostasis

• Bone Remodeling: Ongoing replacement of old bone tissue by new bone tissue.

• Calcium Homeostasis: Regulated by hormones (parathyroid hormone, calcitonin).

• Mechanical and Gravitational Forces: Influence bone density and structure.

Factors Affecting Bones

• Hormonal Abnormalities: Can cause conditions like gigantism, pituitary dwarfism.

• Bone Fractures and Repair: Types include simple, compound, comminuted, etc. Healing involves hematoma formation, fibrocartilaginous callus, bony callus, and remodeling.

• Aging Effects: Decreased bone density, increased risk of fractures.

Axial Skeleton

Overview and Major Divisions

The axial skeleton includes the skull, vertebral column, and thoracic cage. It provides central support and protects vital organs.

• Skull: Composed of cranial and facial bones; includes the nasal septum.

• Vertebral Column:

  • Divided into 5 regions: cervical, thoracic, lumbar, sacral, coccygeal.

  • Number of vertebrae and special features vary by region.

  • Curves of the vertebral column provide flexibility and strength.

  • Disorders: Herniated discs, abnormal curves (scoliosis, kyphosis, lordosis), spina bifida.

• Thorax:

  • Sternum: Breastbone in the center of the chest.

  • Rib Cage: True ribs (attach directly to sternum), false ribs (attach indirectly or not at all).

Table: Types of Epithelial Tissue and Their Locations

Type	Location	Function
Simple Squamous	Alveoli, blood vessels	Diffusion, filtration
Simple Cuboidal	Kidney tubules, glands	Secretion, absorption
Simple Columnar	Digestive tract, uterus	Absorption, secretion
Pseudostratified Columnar	Trachea, upper respiratory tract	Secretion, movement of mucus
Stratified Squamous	Skin, mouth, esophagus	Protection
Transitional	Urinary bladder	Stretching

Key Equations

• Calcium Homeostasis:

$\text{Ca}^{2+} \text{ homeostasis is regulated by:}$ $\text{PTH (parathyroid hormone)} \uparrow \Rightarrow \text{Bone resorption} \uparrow \Rightarrow \text{Blood Ca}^{2+} \uparrow$ $\text{Calcitonin} \uparrow \Rightarrow \text{Bone deposition} \uparrow \Rightarrow \text{Blood Ca}^{2+} \downarrow$

• Bone Growth (Epiphyseal Plate):

$\text{Length of bone} = \text{Rate of cartilage growth} - \text{Rate of cartilage ossification}$

Additional info: Some details, such as the specific names of hormones and the phases of wound healing, were inferred to provide a complete academic context.