AP TEST 2 GUIDE

Tissues Overview

Function and Locations of Junctions

  • Types of Junctions:

    • Tight Junction:

    • Function: Prevents the passage of molecules between cells, allowing for controlled transport.

    • Location: Found in epithelial tissues, such as in the intestines.

    • Desmosome:

    • Function: Provides structural support by anchoring cells together through cytoskeletal elements.

    • Location: Found in tissues subject to stretching, such as cardiac muscle and skin.

    • Gap Junction:

    • Function: Allows for communication between adjacent cells through channels that permit the passage of ions and small molecules.

    • Location: Found in cardiac muscle and smooth muscle tissue.

Major Types of Tissue

Four Major Types of Tissue

  1. Epithelial tissue

  2. Connective tissue

  3. Muscle tissue

  4. Nervous tissue

Epithelial vs. Connective Tissues

Five Characteristics Contrasting Epithelial and Connective Tissues

  • Epithelial tissues:

    • Are avascular

    • Have a high rate of regeneration

    • Exhibit polarity

    • Are closely packed cells with little extracellular matrix

    • Are anchored to the basement membrane

  • Connective tissues:

    • Are vascular with blood supply

    • Typically have a low rate of regeneration

    • Have no polarity

    • Are comprised of various cell types dispersed within the extracellular matrix

    • Are supported by a matrix which may include fibers and ground substance

Classification of Epithelial Tissues

  • Epithelial tissues can be classified by:

    • Shape:

    • Squamous (flat cells)

    • Cuboidal (equal dimensions)

    • Columnar (taller than wide)

    • Layers:

    • Simple (one layer of cells)

    • Stratified (multiple layers of cells)

Naming Epithelial Tissues

  • One layer of flat cells: Simple squamous epithelium

  • Many layers with the top layer of cells taller than they are wide: Stratified columnar epithelium

The Basement Membrane

Definition and Components

  • Basement Membrane: A thin, fibrous extracellular matrix that separates epithelial cells from underlying connective tissue.

  • Contains:

    • Collagen fibers

    • Glycoproteins

    • Proteoglycans

Functions

  • Three Functions of the Basement Membrane:

    1. Provides structural support for the overlying epithelial layer

    2. Acts as a selective barrier to regulate the exchange of materials

    3. Facilitates cell attachment and plays a role in tissue repair

Types and Functions of Epithelial Tissue

  1. Simple Squamous:

    • Location: Alveoli of lungs, lining of blood vessels

    • Function: Filtration, diffusion, and osmosis

  2. Stratified Squamous:

    • Location: Skin, mouth, esophagus

    • Function: Protection against abrasion and bacteria

  3. Pseudostratified Columnar:

    • Location: Lining of respiratory tract

    • Function: Secretion, particularly mucus

  4. Transitional:

    • Location: Urinary bladder

    • Function: Stretching to accommodate fluctuating volumes of liquid

Glands and Tissue Types

Glandular Epithelium

  • Glands are made of epithelial tissue.

Types of Glands

  • Endocrine Glands:

    • Function: Secrete hormones directly into the bloodstream.

    • Example: Thyroid gland

  • Exocrine Glands:

    • Function: Secrete products through ducts to the surface of the skin or to a body cavity.

    • Examples based on secretion types:

    • Mucous glands (secret mucus)

    • Salivary glands (produce saliva)

    • Sweat glands (produce sweat)

  • Unicellular gland example: Goblet cell, found in the intestinal and respiratory tracts

Connective Tissue Overview

Origin and Composition

  • Connective tissue is derived from embryonic tissue called mesenchyme.

  • Contains cells and extracellular matrix consisting of fibers and ground substance.

Cells in Connective Tissues

  • Five Types of Cells and Functions:

    1. Fibroblasts: Produce fibers and ground substance

    2. Macrophages: Engulf foreign materials and help in immune response

    3. Adipocytes: Store fat

    4. Mast cells: Release histamine in response to injury

    5. Chondrocytes: Maintain cartilage matrix

Matrix Components

  • Two Components of Matrix:

    1. Fibers:

    • Support and strength to tissues

    1. Ground Substance:

    • Medium through which cells exchange substances with blood

Types of Fibers

Three Major Types of Fibers

  1. Collagen fibers:

    • Characteristics: Strong, resistant to pulling forces, and provide tensile strength.

  2. Elastic fibers:

    • Characteristics: Stretch and recoil, allowing connective tissues to return to their original shape.

  3. Reticular fibers:

    • Characteristics: Form a supportive network in soft, non-load-bearing organs like the liver and spleen.

Organic Compounds

  • Fibers are made primarily of proteins.

Ground Substances

  • Common Ground Substance:

    • Hyaluronic acid, proteoglycans, glycoproteins

  • Other Types:

    • Glycosaminoglycans (GAGs), chondroitin sulfate, keratan sulfate

Types of Loose Connective Tissue

  • Three Types of Loose Connective Tissue:

    1. Areolar tissue: Contains loose arrangement of fibers and cells, supporting epithelium and organs

    2. Adipose tissue: Contains tightly packed fat cells, functioning as cushioning, insulation, and energy storage

    3. Reticular tissue: Composed of a network of reticular fibers, providing structure to organs like the spleen and lymph nodes

  • Characteristic of 'Loose' Tissues: They have fewer fibers and more ground substance, offering flexibility and cushioning.

Analysis of Various Connective Tissues

  • For each tissue below, specify:

    • Name of cells

    • Extracellular matrix

    • Functions

    • Locations

    • Bleeding on damage:

    • Areolar: Yes

    • Adipose: Yes

    • Reticular: Yes

    • Dense Regular: Yes

    • Dense Irregular: Yes

    • Hyaline Cartilage: No

    • Fibrocartilage: No

    • Bone: Yes

    • Blood: Yes

    • Elastic Cartilage: No

Nourishment of Bone and Cartilage

  • Why do Bone and Cartilage have Lacunae?:

    • They contain mature cells (osteocytes in bone and chondrocytes in cartilage).

  • Nourishment:

    • Bone via blood supply

    • Cartilage through diffusion from surrounding tissues.

  • Cartilage Repair: With poor vascularization, cartilage has a slow repair rate because of limited nutrient supply.

Bone Characteristics

Properties and Functions of Bone

  • Collagen's Contribution: Provides tensile strength and flexibility to bone matrix.

  • Calcium Salts' Contribution: Provide hardness and compressive strength to bone matrix.

Osteon Structure

  • Parts of an Osteon:

    • Central canal

    • Lamellae

    • Lacunae

    • Canaliculi

  • Type: Osteons are a structural component of compact bone.

Unique Characteristics of Connective Tissues

Blood and Cartilage

  • Unique Connective Tissue:

    • Blood: It is liquid, functioning in transportation of nutrients, gases, and waste.

    • Cartilage: It is avascular, providing support without rigidity and allowing flexibility.

Muscle Tissues Overview

Functions and Classifications

  • Main Function of Muscle Tissue:

    • Movement of the body and within the body.

  • Classifications:

    • Skeletal muscle: Voluntary, striated, multi-nucleated, cylindrical shape, found in muscles attached to bones.

    • Smooth muscle: Involuntary, non-striated, single nucleus, spindle shape, found in walls of hollow organs.

    • Cardiac muscle: Involuntary, striated, single or double nucleus, branched shape, found in the heart.

  • Function of Intercalated Discs: Facilitate intercellular communication and synchronous contractions in cardiac muscle.

Nervous Tissue Overview

Components and Functions

  • Neurons: Specialized cells for transmitting impulses.

  • Neuroglia: Supportive cells, protecting and providing support to neurons.

  • Mitosis Differences: Neurons typically do not undergo mitosis, while neuroglia can divide.

  • Space between Neurons and Neuroglia: Contains extracellular fluid and matrix elements.

Tissue Membranes

Components and Types

  • Components of a Membrane:

    • An epithelial layer

    • An underlying connective tissue layer

  • Four Types of Membranes:

    1. Mucous Membrane:

    • Epithelium: Varies based on location

    • Connective Tissue: Lamina propria

    • Location: Lines body cavities open to the exterior

    1. Serous Membrane:

    • Epithelium: Simple squamous

    • Connective Tissue: Loose areolar tissue

    • Location: Lines closed body cavities (e.g., thoracic cavity)

    1. Cutaneous Membrane: Skin, composed of keratinized stratified squamous and dense irregular connective tissue

    2. Synovial Membrane:

    • Epithelium: Lacks basal lamina, contains synoviocytes

    • Location: Lines joint cavities

  • Epithelium in Synovial Membrane: No true epithelium; it is a modified connective tissue.

Serous Membranes

Examples

  1. Pleura (lungs)

  2. Pericardium (heart)

  3. Peritoneum (abdominal cavity)

Tissue Repair Process

  1. Inflammation: Initial response to tissue damage, involves swelling and increased blood flow.

  2. Granulation Tissue Formation: New connective tissue and blood vessels form during healing.

  3. Regeneration or Fibrosis: Depending on the tissue, it either regenerates or forms scar tissue.

Tissue Types

  • Stromal Cells: Supportive tissue cells.

  • Parenchymal Cells: Functional cells of an organ.

  • Repair by Fibroblasts in Cardiac Muscle: May lead to scarring and impaired function healing.

Skin Overview

Functions

  1. Protection against pathogens

  2. Regulation of body temperature

  3. Sensing the environment

  4. Synthesis of Vitamin D

Vitamin D Function

  • Essential for calcium absorption and bone health.

Blood Reservoir

  • The skin can store a significant volume of blood in its vascular network.

Skin Structure

Protective Epithelium

  • The skin consists of keratinized stratified squamous epithelium.

  • Keratin: A tough fibrous protein found in the skin, providing water resistance and protection.

Epidermal Cell Layers

  • Superficial layer of epidermal cells: Stratum corneum, contains dead keratinized cells.

  • Deep layer of epidermal cells: Stratum basale, where new cells are generated.

Epidermal Cells Overview

  1. Keratinocytes: Primary cell type producing keratin.

  2. Tactile (Merkel) Cells: Sensory receptors for touch.

  3. Langerhans Cells (Dendritic Cells): Immune defense against pathogens.

Dermis Structure

Layers

  1. Papillary Layer: Contains loose areolar connective tissue, with dermal papillae enhancing surface area for nutrient exchange.

  2. Reticular Layer: Composed of dense irregular connective tissue, providing strength and elasticity.

Hypodermis

  • Contains adipose and loose connective tissues, serving as insulation and cushioning.

  • Note: Hypodermis is not technically part of the skin but is integral to its function.

Skin Pigmentation

Pigments and Locations

  1. Melanin: Primarily in the epidermis, provides skin color and UV protection.

  2. Carotene: Accumulates in the subcutaneous tissue and stratum corneum, contributing to yellow-orange hue.

  3. Hemoglobin: Red pigment in blood vessels, influencing skin tone.

Condition Overview

  • Vitiligo: Loss of melanocytes causing patchy skin coloration.

  • Cyanosis: Blue coloration due to poorly oxygenated blood.

Hair Structure

Parts of Hair

  • Above Epidermis: Shaft

  • Below Epidermis: Hair root, including hair bulb

  • Apical Meristem: Region of dividing cells that produces new hair growth.

  • Composition: Hair is made of keratin.

  • Hair Papilla: Contains blood vessels nourishing hair follicle.

  • Muscle Attachment: Arrector pili muscle, causing hair to stand when cold or frightened.

Sebaceous and Sudoriferous Glands

Sebaceous Glands

  • Secretion: Sebum, an oily substance for moisture and protection

  • Location: Found near hair follicles.

  • Secretion Type: Holocrine secretion (cell explodes to release contents).

Sudoriferous (Sweat) Glands

  1. Eccrine Glands: Most commonly found, regulating temperature through sweat.

  2. Apocrine Glands: Found in specific areas, secreting thicker sweat associated with scent.

Maintaining Body Temperature

Skin Functions

  1. Vasodilation: Expanding blood vessels to release heat.

  2. Sweating: Evaporative cooling through sweat secretion.

Nail Structure

Composition

  • Made of Keratin: Provides strength and protection.

  • Nail Matrix: Dividing area for nail growth.

Nail Color

  • Nails appear pink due to underlying blood vessels in the dermis.

Bone Overview

Bone Characteristics

  • Femur Replacement: Bones continuously remodel but don’t completely replace, maintaining structural integrity.

  • Minerals: Important for bone strength include calcium, phosphorus, and magnesium.

Functions of Long Bones

  1. Medullary Cavity: Stores bone marrow for blood cell production.

  2. Periosteum: Protects bone, serves as muscle attachment.

  3. Endosteum: Lines medullary cavity, involved in bone growth and repair.

  4. Epiphysis with Spongy Bone: Provides strength without weight.

  5. Epiphyseal Cartilage/Plate: Allows for elongation during growth.

Bone Structure

Blood Cell Production

  • Red Bone Marrow Functions: Produces red blood cells, white blood cells, and platelets.

Periosteum Structure

  • Two Layers:

    1. Outer Fibrous Layer: Provides attachment to muscles.

    2. Inner Osteogenic Layer: Contains bone-forming cells.

Vascularization in Bone Structure

Blood Vessels and Nerves

  • Presence of Blood Vessels: Yes, for nourishment and signaling.

Cartilage in Bone

  • Child’s Long Bones: Hyaline cartilage present at growth plates and joint surfaces.

Bone Matrix Composition

Major Components

  1. Collagen: Provides tensile strength.

  2. Hydroxyapatite: Mineral component providing hardness.

Bone Cell Types

  • Four Cell Types:

  1. Osteoblasts: Bone-forming cells.

  2. Osteocytes: Mature bone cells maintaining the matrix.

  3. Osteoclasts: Bone-resorbing cells for remodeling.

  4. Bone Lining Cells: Involved in the maintenance of bone surface.

Relation Among Bone Cells

  • Osteoblasts, osteocytes, and osteoclasts are related; Bone Lining Cells serve a different role.

Calcium Regulation in Bones

Cell Activation

  • Osteoclasts become active when blood calcium levels are low, breaking down bone matrix to release calcium.

Types of Bone Tissue

Two Types

  1. Compact Bone: Dense, providing structural strength.

  2. Spongy Bone: Lighter, with a mesh-like structure facilitating nutrient access.

Histological Differences

  • Compact bone is dense and organized into osteons; spongy bone is less organized with trabecular structure.

Bone Canal Systems

Comparison of Canals

  • Perforating (Volkmann’s) Canal: Connects blood vessels from the periosteum to central canals in bone.

  • Central (Haversian) Canal: Contains blood vessels and nerves in the center of osteon.

Bone Growth Types

Growth Processes

  • Appositional Growth: Increases bone diameter by adding bone on the outer surface.

  • Interstitial Growth: Increases bone length by replacing cartilage with bone at growth plates.

Bone Formation Processes

Types of Bone Ossification

  1. Intramembranous Ossification: Forms flat bones (e.g., skull).

  2. Endochondral Ossification: Replaces hyaline cartilage with bone (e.g., long bones).

Initiation of Bone Formation

  • Begins at primary ossification centers in diaphysis for endochondral ossification.

Secondary Ossification Centers

  • Located in epiphyses of long bones, contributing to growth after birth.

Remaining Cartilage Post-Ossification

  • Epiphyseal plate and articular cartilage remain as hyaline cartilage.

Radiological Evaluation of Bone Growth

X-Ray Usage

  • Radiologists assess growth and development by examining epiphyseal plates in carpal bones to estimate age.

Bone Growth Length Dynamics

  • Length Growth: Bone grows at the epiphyseal plate (diaphyseal side becomes bone).

  • End of Length Growth: Occurs after puberty when growth plates fuse.

Bone Widening Growth Dynamics

  • Width Growth: Involves appositional growth, adding bone to outer layers.

  • End of Width Growth: Width can grow throughout lifetime, particularly around stress and use.

Hormonal Regulation of Calcium

Hormones Involved

  • Parathyroid Hormone (PTH): Increases blood calcium levels by stimulating osteoclast activity.

  • Calcitonin: Decreases blood calcium levels by inhibiting osteoclast activity.

Fracture Repair Stages

Major Steps

  1. Hematoma formation (blood clot)

  2. Soft callus formation (fibrocartilage)

  3. Hard callus formation (bony callus)

  4. Remodeling phase to restore strength and structure.

Fracture Commonality

  • Colles’ fractures and clavicular fractures are common due to specific areas of vulnerability during falls or accidents.

Types of Fractures

  1. Greenstick Fracture: An incomplete fracture typically seen in children.

  2. Compound Fracture: An open fracture where the bone breaks through the skin.

Skeletal System Overview

Skull Overview

  • Large foramen in the occipital bone for the spinal cord entry, forming a joint with the atlas (C1) allowing for nodding movement.

Scapula Connection

  • The scapula is connected to the axial skeleton via the clavicle.

Joint Composition in Limbs

Joint Structures

  • Elbow: Humerus and ulna

  • Wrist: Radius, scaphoid, lunate

  • Knee: Femur, tibia, patella

  • Hip: Femur and coxal bone

  • Shoulder: Humerus and scapula

  • Ankle: Tibia, fibula, and talus

Specific Bone Articulations

Coxal Joint Overview

  • Coxal bone articulates with the sacrum, forming a large basin with the vertebral column for support.

Fibula and Femur Joint Composition

  • Proximal End of Tibia: Articulates with femur and fibula.

Hyoid and Cranial Bone Articulations

  • Hyoid does not articulate with other bones; serves as an attachment for muscles.

  • The only movable joint in the skull is the temporomandibular joint (TMJ), formed by the mandible and temporal bone.

Articulation Questions in Vertebral Column

  • Cervical, Thoracic, Lumbar Distribution: 7 Cervical, 12 Thoracic, 5 Lumbar.

  • Caudal Bones: Sacrum and coccyx.

Intervertebral Discs Structure

  • Parts:

    • Annulus Fibrosus (outer layer)

    • Nucleus Pulposus (inner gel-like substance)

  • No blood vessels present in the intervertebral discs.

  • Herniated Disc: Condition where the nucleus pulposus protrudes through the annulus, causing pain.

Curvature Development in Vertebral Column

Primary and Secondary Curves

  • Primary Curves: Present at birth (thoracic and sacral).

  • Secondary Curves: Develop as the child grows to support upright posture (cervical and lumbar).

  • Abnormal Curves:

    • Lordosis: Excessive lumbar curve.

    • Kyphosis: Excessive thoracic curve.

    • Scoliosis: Lateral curvature of the spine.

Vertebral Foramen

Functions

  • Centers for protection of spinal cord. Each vertebra has an opening (foramen) to allow for passage of spinal nerves.

  • Intervertebral Foramina: Lateral openings for spinal nerves to exit the vertebral column.

Bone Types Classification

Shapes of Bones

  • Long Bones: Humerus, femur

  • Short Bones: Carpals, tarsals

  • Flat Bones: Sternum, scapula

  • Irregular Bones: Vertebrae, hyoid

Bone Articulations and Connection

Joint Compositions

  • Clavicle: Articulates with sternum and scapula.

  • Scapula: Does not articulate directly with ribs.

  • Humerus: Articulates with glenoid cavity of scapula, and at the elbow with the radius and ulna.

Carpals and Phalanges Overview

Carpal Bone Names

  • Scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate.

  • Total phalanges in one hand: 14.

  • Pollex: Thumb.

  • Hallux: Big toe.

Key Structural Features

Structures of Pelvis

  • Os Coxae: Composed of ilium, ischium, pubis

  • Joint Association: Femur articulates with acetabulum of coxal bones.

  • Distal End of Tibia: Articulates with the talus and fibula.

Tarsal Bone Structures

  • Seven Tarsal Bones Include:

    1. Talus

    2. Calcaneus

    3. Navicular

    4. Medial cuneiform

    5. Intermediate cuneiform

    6. Lateral cuneiform

    7. Cuboid

Bone Repair Processes

Steps in Repair

  1. Hematoma: Blood forms a clot at the fracture site.

  2. Soft Callus Formation: Fibroblasts create a cartilaginous bridge.

  3. Hard Callus Formation: Osteoblasts replace soft callus with spongy bone.

  4. Remodeling: Bone is reshaped and strengthened over time.

Key Bones to Remember

  • Facial Bones: Include nasal, maxilla, mandible

  • Cranial Bones: Include frontal, parietal, occipital

  • Carpals/Metacarpals: Key bones in the wrist and hand.

  • Learn the articulation and sutures between these bones to understand their anatomy better.