HUMAN ANATOMY AND PHYSIOLOGY (PRELIMS) (1)

HUMAN ANATOMY AND PHYSIOLOGY

Leonardo da Vinci initiated the study of the human body through drawings and diagrams.

DEFINITION

• Ana-Tome: Greek for "cutting up."
• Anatomy: The study of the structure of body parts and their relationships.

SUBDIVISIONS OF ANATOMY

GROSS ANATOMY

• Regional: Study of all structures in a specific body part (e.g., abdomen, leg).
• Systemic: Study of the body's gross anatomy by system.
• Surface: Study of internal structures as they relate to the overlying skin.

MICROSCOPIC ANATOMY

• Cytology: Study of cells.
• Histology: Study of tissues.

DEVELOPMENTAL ANATOMY

• Embryology: Study of the body's developmental changes before birth.

SPECIAL BRANCHES OF ANATOMY

• Pathological: Study of structural changes caused by disease.
• Radiographic: Study of internal structures visualized by X-rays.
• Molecular: Study of anatomical structures at a subcellular level.

PHYSIOLOGY

Study of the function or behavior of the body's organs or structures.

PATHOLOGY

Study of disease, its causes, and its effects on the body.

MEDICAL TERMINOLOGY

Basic Anatomical Terminology

CEPHALIC (HEAD)

• Frontal (forehead)
• Temporal (temple)
• Cranial (skull)
• Occipital (base of skull)
• Facial (face)
• Orbital or ocular (eye)
• Otic (ear)
• Buccal (cheek)
• Nasal (nose)
• Oral (mouth)
• Mental (chin)

CERVICAL (NECK)

TRUNK

• Sternal (breastbone)
• Thoracic (chest)
• Mammary (breast)
• Abdominal (abdomen)
• Umbilical (navel)
• Pelvic (pelvis)
• Pubic (pubis)
• Dorsal (back)
• Scapular (shoulder blade)
• Vertebral (spinal column)
• Lumbar (loin, between hips)
• Sacral
• Coccygeal (tailbone)
• Gluteal (buttock)
• Perineal (region between anus and external genitals)

UPPER LIMB

• Acromial (shoulder)
• Axillary (armpit)
• Brachial (arm)
• Antecubital (front of elbow)
• Antebrachial (forearm)
• Carpal (wrist)
• Manual (hand)
• Palmar or volar (palm)
• Digital or Phalangeal (fingers)
• Pollex (thumb)
• Dorsum (back of hand)

LOWER LIMB

• Coxal (hip)
• Inguinal (groin)
• Femoral (thigh)
• Patellar (anterior surface of knee)
• Popliteal (hollow behind knee)
• Crural (leg/calf)
• Tarsal (ankle)
• Pedal (foot)
• Digital or Phalangeal (toes)
• Hallux (great toe)
• Dorsum (top of foot)
• Plantar (sole)
• Calcaneal (heel)

Nine Regions of the Abdomen

The abdomen is delineated into nine regions by four planes for descriptive and diagnostic purposes; these regions contain superficial organs.

Other Body Cavities:

• Oral and digestive: The oral cavity (mouth) contains teeth and tongue and is continuous with the digestive organs, opening to the exterior at the anus.
• Nasal: Located within and posterior to the nose; part of the respiratory system passageways.
• Orbital: Orbits in the skull house the eyes.
• Middle ear: Cavities in the skull medial to the eardrums containing bones that transmit sound vibrations.

Anatomical Position

A standardized method of observing the body for consistent anatomical references:

• Standing upright
• Facing the observer, head level
• Eyes facing forward
• Feet flat on the floor
• Arms at the sides
• Palms turned forward (vertical)

Positions and Directions

Terms describing the position of one body part relative to another, usually along the three major body planes:

• Superior: Closer to the head or higher.
• Inferior: Closer to the feet or lower.
• Anterior: More in front.
• Posterior: More in back.
• Medial: Closer to the midline.
• Lateral: Farther from the midline.
• Proximal: Closer to the root of the limb (extremities only).
• Distal: Further from the root of the limb (extremities only).
• Superficial: Closer to the body's surface.
• Deep: Closer to the body's core.
• Ventral: Towards the front or belly.
• Dorsal: Towards the back.
• Prone: Lying face down.
• Supine: Lying face up.
• Unilateral: Pertaining to one side of the body.
• Bilateral: Pertaining to both sides of the body.

Basic Body Planes or Sections

Planes or sections that cut the body, organs, tissues, or cells to obtain a three-dimensional perspective.

• Sagittal Plane: Divides the body into right and left portions. Midsagittal or median planes divide the body into equal halves.
• Frontal Plane: Divides the body into front and back portions; also called the Coronal plane.
• Transverse Plane: Divides the body into upper and lower portions; also called the Horizontal plane.

Anatomical Terminology

• Head: expanded end of a part of the body (e.g., head of pancreas, head of radius).
• Little Head: capitulum (l) a small head (from capcut = head + ulum + little) (e.g., capitulum of humerus, since it already has one head).
• Neck: cervix or collum (l) the constricted part of a structure adjacent to the head of it (e.g., neck of radius, neck (cervix) of the uterus).
• Body: corpus (l) the principal part of a structure or the shaft of a long bone; body of pancreas; body of a vertebra radius, corpse = body.
• Tail: cauda (l) the tapered end of a structure, the tail of the pancreas.
• Lobe: lobus (l) a subdivision of an organ or structure e.g a lobe of the lung, liver etc.
• Lobule: lobulus (l) a subdivision of a lobe (lobe + ulus = little ) e.g lobule of lung. Liver, etc.
• Segment: segmentum (l) a unit of structure, separated from other segments, with its own blood supply, segment of love of a lung; with its on bronchus, a branch of a lobar bronchus and its own blood vessels.
• Extremity: extremitas (l) the end of long structure extremity of kidney, of a bone, etc. In (NA) not used referring to a limb of the body,
• Apex: the pointed end of a structure of lung.
• Base: the broad flattened end of a structure, often its lower end base of the lung.
• Aperture: hole or opening.
• Foramen: hole or opening = foramina.
• Hiatus: opening or gap; esophageal hiatus.
• Orifice: an opening; mitral orifice of heart.
• Os: an opening or mouth; oral hygiene, pl.ossa.
• Ositium: an opening; cardiac ostium of stomach pl. Ostia.
• Lumen: a window or opening; usually refers to the cavity of a hollow organ, stomach, artery, etc.
• Fissure: fissura, a narrow slit, cleft or groove; e.g fissures of the lung, liver, brain.
• Fossa: (l) a depression or hollow below the normal surface of a structure, a trench, ditch, e.g pituitary fossa, cranial fossa (pl. hila)
• Hilus: hilum; an indentation or depression on the surface of an organ, where vessels enter or leave the organ e.g hilum of lung, kidney, lymph node (pl.hila)
• Sulcus: (l) - a groove or furrow, broader than a fissure sometimes has a tendon or artery, etc. running along it e.g intertubercular (bicipital) groove of humerus, central sulcus of cerebrum, pl. Sulci.
• Insicura: (l) a notch or cleft e.g incisura angularis notch of stomach p.l insecure
• Meatus: (l) a canal or tubelike passage e.g the external acoustic (auditory) meatus of the ear.
• Ramus: a branch of division of a vessel, nerve or bone e.g ramus of the mandible, anterior ramus of a spinal nerve, etc pl.rami
• Septum: (l) a partition separating two cavities, e.g nasal septum, interatrial of heart.

Movements

• Flexion: Bending a joint or decreasing the angle between two bones.
• Extension: Straightening a joint or increasing the angle between two bones.
• Hyperextension: Excessive extension beyond the anatomical position.
• Adduction: Moving a body part towards the midline.
• Abduction: Moving a body part away from the midline.
• Pronation: Turning the arm or foot downward (palm or sole down).
• Supination: Turning the arm or foot upward (palm or sole up).
• Retraction: Moving a part backward.
• Protraction: Moving a part forward.
• Elevation: Raising a part.
• Depression: Lowering a part.
• Rotation: Turning on a single axis.
• Circumundation: Tri-planar circular motion at the hip or shoulder.
• Internal rotation: Rotation of the hip or shoulder toward the midline.
• External rotation: Rotation of the hip or shoulder away from the midline.
• Lateral Flexion: Side bending left or right.
• Inversion: Turning the sole of the foot inward.
• Eversion: Turning the sole of the foot outward.
• Dorsiflexion: Ankle movement bringing the foot toward the shin.
• PlantarFlexion: Ankle movement pointing the foot downward.
• Radial Deviation: Movement of the wrist towards the radius.
• Ulnar Deviation: Movement of the wrist towards the ulnar.
• Opposition: Movement of the thumb across the palm.

CELLS

Cell Theory

1. The cell is the basic structural and functional unit of living organisms.
2. The activity of an organism depends on the collective activities of its cells.
3. The biochemical activity of cells is dictated by their shape or form and by the relative number.
4. Continuity of life has a cellular basis.

Anatomy of a Generalized Cell

• Nucleus: Control center containing DNA.
• Cytoplasm: Material outside the nucleus and inside the plasma membrane.
• Plasma membrane: Barrier for cell contents.

NUCLEUS

Nuclear Membrane

• Double phospholipid membrane with nuclear pores for exchange of material.

Nucleoli

• Sites of ribosome production.

Chromatin

• Unwound DNA and protein that condenses to form chromosomes during cell division.

PLASMA MEMBRANE

• Semi-permeable, double phospholipid layer with hydrophilic heads and hydrophobic tails.
• Contains proteins, cholesterol, and glycoproteins for various functions.
• Cells are bound together by:
  • Glycoproteins.
  • Wavy contours.
  • Special membrane junctions

CYTOPLASM

• Cytosol: Fluid containing nutrients dissolved in water.
• Organelles: Metabolic machinery of the cell.
• Inclusions: Non-functioning units that store nutrients.

Mitochondria

• Powerhouse of the cell; produces ATP.

Ribosomes

• Sites of protein synthesis.

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes; site of membrane building materials.
• Smooth ER: Functions in cholesterol synthesis, fat metabolism, and detoxification.

Golgi Apparatus

• Modifies and packages proteins into secretory vesicles and cell membrane components.

Lysosomes

• Contain hydrolytic enzymes for digesting non-usable materials.

Peroxisomes

• Membranous sacs of oxidase enzymes for detoxification.

Cytoskeleton

• Provides internal framework and determines cell shape.

• Three different types:

  • Microfilaments - cell motility and changed in cell shape - actin and myosin
  • Intermediate filaments - help form desmosomes and internal guy wires.
  • Microtubules - determine overall shape of a cell and location of organelles.

Centrioles

• Direct formation of mitotic spindle during cell division.

Cellular Extensions

• Cilia: Moves materials across the cell surface.
• Flagella: Propels the cell.
• Microvilli: Tiny extensions of the plasma membrane that project from an exposed cell surface.

Role of RNA

Transfer RNA (tRNA)

Transfers appropriate amino acids to the ribosome for building protein.

Ribosomal RNA (rRNA)

Helps form the ribosomes along with proteins where proteins are built.

Messenger (mRNA)

Carries the instructions for building a protein from the nucleus to the ribosome.

Cell Life Cycle

Interphase

• Cell grows and carries on metabolic processes.

Cell division

• Cell replicates itself for growth and repair.

DNA Replication

• Occurs toward the end of interphase.
• DNA uncoils and each side serves as a template.

Events of Cell Division

Mitosis

• Division of the nucleus.

Cytokinesis

• Division of the cytoplasm.

Stages of Mitosis

Interphase

• No cell division occurs; normal metabolic activity.

Prophase

• Centromeres migrate to the poles and direct the assembly of the spindle.

Metaphase

• Chromosomes are aligned in the center of the cell.

Anaphase

• Daughter chromosomes are pulled toward the poles; cell elongates.

Telophase

• Daughter nuclei begin forming; cleavage furrow forms.

Cytokinesis

• Division of the cytoplasm, resulting in two daughter cells.

Protein Synthesis

• Gene: DNA segment that carries a blueprint for building one protein.
• RNA is essential for protein synthesis.

Transcription

• Transfer of information from DNA to mRNA.

Translation

• Base sequence of mRNA is translated to an amino acid sequence based on codon/anticodon complements.

BODY TISSUES

Four Primary Tissue Types

• Epithelium: Covering.
• Connective tissue: Support.
• Nervous Tissue: Control.
• Muscle: Movement.

Epithelial Tissues

• Functions: protection, absorption, filtration, secretion.

Epithelium Characteristics

• Cells fit closely together.
• One free surface.
• Bound by a basement membrane.
• Avascular.
• Regenerate easily.

Classification of Epithelium

• Number of cell layers: simple (one layer), stratified (more than one layer).
• Shape of cells: squamous (flattened), cuboidal (cube-shaped), columnar (column-like).

Simple Epithelium

• Simple squamous: single layer of flat cells; where filtration or exchange occurs.
• Simple cuboidal: single layer of cube-like cells; common in glands and kidney tubules.
• Simple columnar: single layer of tall cells; lines digestive tract.
• Pseudostratified columnar: single layer, but some cells are shorter; sometimes ciliated.

Stratified Epithelium

• Stratified squamous: cells at the free edge are flattened; protective covering.
• Stratified cuboidal & columnar: Rare in human body; found mainly in ducts of large glands.
• Transitional epithelium: shape depends on stretching; lines urinary system organs.

Glandular Epithelium

• Gland: one or more cells that secrete a particular product.

• Two major gland types:

  • Endocrine gland: Ductless; secrete hormones into blood.
  • Exocrine gland: Empty through ducts to the epithelial surface; include sweat and oil glands.

Connective Tissue

• Functions: binds body tissues, supports the body, provides protection.

Connective Tissue Characteristics

• Variations in blood supply.
• Extracellular matrix: non-living material that surrounds living cells.

Elements of the Matrix

• Ground substance: water along with adhesion proteins and polysaccharide molecules.
• Fiber:Produced by the cells
  • Collagen fibers
  • Elastic fibers
  • Reticular fibers

Types of Connective Tissue

• Bone (osseous tissue): bone cells in lacunae, hard matrix of calcium salts, collagen fibers.
• Hyaline cartilage: abundant collagen fibers, rubbery matrix; fetal skeleton.
• Fibrocartilage: highly compressible; cushion-like disc between vertebrae.
• Elastic cartilage: elasticity; supports the external ear.
• Dense connective tissue: collagen fibers; tendons & ligaments.
• Adipose tissue: lipid deposits; insulates the body, protects organs, fuel storage.
• Reticular connective tissue: interwoven fibers; internal supporting network of lymphoid organs.
• Blood: blood cells surrounded by fluid matrix; transport vehicle of materials.
• Loose Connective Tissue types: Areolar, Adipose, Reticular.

Muscle Tissue

• Function is to produce movement by contracting and shortening.

Three Types of Muscle Tissue

• Skeletal muscle, Cardiac muscle, Smooth muscle

Muscle Tissue Types

• Skeletal muscle:

  • Can be controlled voluntarily
  • Cells attach to connective tissue
  • Cells are striated
  • Cells have more than one nucleus

• Cardiac Muscle:

  • Found only in heart
  • Function is to pump blood (involuntary)
  • Cells attached to other cardiac muscle cells at intercalated disks
  • Cells are striated
  • One nucleus per cell

• Smooth muscle - visceral muscle:

  • Involuntary muscle
  • Surrounds hollow organs
  • Attached to other smooth muscle cells
  • No visible striation
  • One nucleus per cell
  • Spindle shaped

Nervous tissue

• Neurons and nerve supporting cells (those that insulate, support and protect neutrons)
• Function is to receive and send impulses to other areas of the body
  • Irritability
  • Conductivity

Tissue Repair (Wound Healing)

• Regeneration: replacement of destroyed tissue by the same kind of cells.
• Fibrosis: repair by dense fibrous connective tissue (scar tissue).
• Determination of method: type of tissue damaged, severity of the injury.

Events in Tissue Repair

• Capillaries become very permeable
  • Introduce clotting proteins to make clot
  • Wall of injured area to prevent blood loss and infection
• Formation of granulation tissue
  • Contains capillaries and phagocytes
• Regeneration of surface epithelium just below the scab

Regeneration of Tissues

• Tissue that regenerate easily
  • Epithelial tissue
  • Fibrous connective tissue and bone
• Tissues that regenerate poorly
  • Skeletal muscle
• Tissues that are replaced largely with scar tissue
  • Cardiac muscle
  • Nervous tissue within the brain and spinal cord

Developmental Aspects of Tissue

• Epithelial tissue arises from all three primary germ layers
• Muscle and connective tissue arise from the mesoderm
• Nervous tissue arises from the ectoderm
• With old age there is a decrease in mass and viability in most tissue

SKIN AND BODY MEMBRANES

• Function
  • Line or cover body surfaces
  • Protect body surface
  • Lubricate body surface

Epithelial Membranes

• Cutaneous membrane = skin
  • A dry membrane
  • Outermost protective boundary
    • Superficial epidermis
      • Keratinized stratified squamous epithelium
    • Underlying epidermis
      • Mostly dense connective tissue
• Mucous membrane
  • Surface epithelium
    • Type depends on site
  • Underlying loose connective tissue (lamina propria)
  • Lines all body cavities that open to the exterior body surface
  • Often adapted for absorption or secretion
• Serous membrane
  • Surface simple squamous epithelium
  • Underlying areolar connective tissue
  • Lines open body cavities that are closed to the exterior of the body
  • Serous layers separated by serous fluid

Specific Serous Membranes

• Peritoneum - Abdominal cavity
• Pleura - Around the lungs
• Pericardium - Around the heart

Connective Tissue Membrane

Synovial membrane

• Connective tissue only
• Lines fibrous capsules surrounding joints

Integumentary System

• Skin (cutaneous membrane)
• Skin Derivatives
  • Sweat gland
  • Oil glans
  • Hairs
  • Nails
    Skin Functions
  • Protects deeper tissues from:
    • Mechanical damage
    • Chemical damage
    • Bacterial damage
    • Thermal damage
    • Ultraviolet radiation
    • Dessication
    • Aids in heat regulation
    • Aids in excretion of urea and uric acid
    • Synthesizes vitamin D
      Skin Structure
  • Epidermis - outer layer
    • Stratified squamous epithelium
    • Often keratinized (hardened by keratin)

Layers of epidermis

• Stratum basale
  * Cells undergoing mitosis
  * Lies next to dermis
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
  * Occurs only in thick skin
• Stratum corneum
  * Shingle like dead cells

Melanin

• Pigment (melanin) produced by melanocytes

• Color is yellow to black

• Melanocytes are mostly in the stratum basale

• Amount of melanin produced depends upon genetic and exposure to sunlight

  Skin Color Determinants

  • Melanin
    • Yellow, brown or black pigments
  • Carotene
    • Orange-yellow pigment from some vegetables
  • Hemoglobin
    • Red coloring from blood cells in dermis capillaries
    • Oxygen content determines the extent or red coloring
    • Cyanosis - low oxygen creates a bluish appearance

Dermis (two Layers)

• Papillary Layer
  • Projections called dermal papillae
  • Pain receptors
  • Capillary loops
• Reticular Layer
  • Blood vessels
  • Glands
  • Nerve receptors

Skin Structure

• Hypodermis - deep to dermis
  • Not part of the skin
  • Anchors skin to underlying organs
  • Composed mostly of adipose tissue

Appendages of the Skin

• Sebaceous gland * Produce oil * Lubricant for skin * Kills bacteria * Most with ducts that empty into hair follicles * Glands are activated at puberty
  • Sweat glands
  • Widely distributed in the skin Two types:
    • Eccrine
      • Eccrine sweat gland
      • Open via duct to pore on skin surface
    • Apocrine
      • Apocrine sweat gland
      • Ducts into hair follicles
        Sweat And It’s Function
• Composition
  • Mostly water
  • Some metabolic waste
  • Fatty acids and proteins (apocrine only)
• Function
  • Helps dissipate heat
  • Excretes waste products
  • Acidic nature inhibits bacteria growth
• Odor is from associated bacteria

Appendages of the skin

• HAIR * Produced by hair bulb * Consists of hard keratinized epithelial cells * Melanocytes provide pigment for hair color
  • NAILS
    • Scalelike modifications of the epidermis
    • Heavily keratinized
    • Stratum basale extends beneath the nail bed
    • Responsible for growth
    • Lack of pigment makes them colorless

Skin Homeostatic Imbalances

Infections

• Athlete's foot - caused by fungal infections
• Boils and carbuncles - caused by bacterial infection
• Cold sores - Caused by virus

Infections and allergies

• Contact dermatitis - exposures causes allergic reaction
• Impetigo - caused by bacterial infection
• Psoriasis - cause is unknown, triggered by trauma, infection, stress

Burns

• Tissue damage and cell death caused by heat, electricity, UV Radiation or chemicals Associated dangers:
  • Dehydration
  • Electrolyte imbalance
  • Circulatory shock

RULES OF NINES Way to determine the extent of burns:

• Body is divided into 11 areas for quick estimation
• Each area represents about 9 percent

Severity of Burns
* First degree burns
* Only epidermis is damaged
* Skin is red and swollen
* Second degree burns
* Epidermis and upper epidermis are damaged
* Skin is red with blisters
* Third degree burns
* Destroy entire skin layer
* Burn is gray-white or black
* Burns are considered critical if:
* Over 25% of body has second degree burns
* Over 10% of the body has third degree burns
* There are third degree burns of the face, hands or feet

Skin Cancer

• Cancer - abnormal cell mass

  • Two types:
    • Benign - does not spread (encapsulated)
    • Malignant
      Metastasized (moves) to other parts of the body
    • Skin cancer is the most common type of cancer

Skin cancer types

• Basal cell carcinoma * Least malignant * Most common type Arises from stratum basale
  • Squamous cell carcinoma Arises from stratum spinosum Metastasizes to lymph nodes
    • Early removal allows a good chance of cure
• Malignant melanoma
  * Most deadly of skin cancer
  * Cancer of melanocytes
  * Metastasizes rapidly to lymph and blood vessels
  * Detection uses ABCD rule

ABCD RULE

• A = Asymmetry * Two sides of pigmented mole do not match
  • B = Border
    • Borders of mole are not smooth
• C = Color * Different colors in pigmented area
  • D = Diameter
    • Spot is larger than 6mm in diameter

SKELETAL SYSTEM

• Provides an internal framework for the body, protects organs by enclosure and anchors skeletal muscles so that muscle contraction can cause movement.

Appendicular VS Axial

• Axial - the bones that form the longitudinal axis of the body
• Appendicular - bones of the limbs and girdies that are “appended”(attached) to the axial skeleton
• JOINTS - Give the body flexibility and allow movement to occur.
• CARTILAGE - It is firm tissue but is softer and much more flexible than bone.
• LIGAMENTS - Fibrous cords that bind the bones together and joints.

Functions of the Bones

• Protects internal organs
• Stores and releases fat
• Produce blood cells
• Stores and releases minerals
• Facilities movement
• Supports the body

Classification of Bones

• Compact bone - dense and looks smooth and homogenous
• Spongy bone - composed of small needle like pieces of bone and lots of open space
• Long bones -
  • longer than they are
  • They are mostly compact bone
  • Have a shaft with heads or both ends
• Short bones - generally cube-shaped and contain mostly spongy bone
• Flat bones -
  • Thind, flattened and usually curved
  • Have two thin layers of compact bone sandwiching a layer of spongy bone between them

Osteon (Haversian system)

Microscopic Anatomy of Bone

• Lamellae: Concentric rings of bone matrix.
• Central (Haversian) canal: Contains blood vessels and nerves.
• Lacunae: Spaces containing osteocytes.
• Canaliculi: Tiny canals connecting lacunae.
• Volkmann's canals: Perpendicular canals connecting Haversian canals.

Microscopic Anatomy

Projections that are sites of muscle and ligament attachment

• Tuberosity
• Crest
• Trochanter
• Line
• Tubercle
• Epicondyle
• Spine
• Process

Projections that help to form joints

• Head
• Facet
• Condyle
• Anterior

Bone Formation, Growth and Remodeling

The bones in embryos are primarily hyaline cartilage. During development, much of this cartilage is replaced by bone. Cartilage remains in isolated areas, such as the bridge of the nose, parts of ribs, and joints.
Bone growth occurs at epiphyseal plates, allowing for growth of long bones during childhood. New cartilage is continuously formed, and older cartilage becomes ossified. Cartilage is broken down, and bone replaces cartilage.

Rickets

• Disease of a child in which the bones fail to calcify. As a result, the bones soften, and the weight-bearing bones of the legs show a definite bowing. Usually due to a lack of calcium in the diet or lack of Vitamin D. which is needed to absorb calcium into the bloodstream.

Stages in the Healing of a Bone Fracture

1. Hematoma forms: Blood vessels rupture when the bone breaks, resulting in a blood-filled swelling called a hematoma. Deprived of nutrition, bone cells die.

2. Fibrocartilage callus forms: Growth of new capillaries and disposal of dead tissues by phagocytes occur. Connective tissue cells form a fibrocartilage callus containing cartilage matrix, bony matrix, and collagen fibers, acting as a “splint” closing the gap

3. The bony callus forms: Osteoblasts and osteoclasts migrate to the area and multiply, and the fibrocartilage callus is gradually replaced by a bony callus made of spongy bone.

4. Bone remodeling occurs: The bony callus is remodeled in response to mechanical stresses, forming a strong, permanent “patch” at the fracture site.

The Axial Skeleton

The axial skeleton forms the longitudinal part of the body and is divided into three parts:

1. Skull (cranium and facial bones)

2. Hyoid bone (anchors tongue and muscles associated with swallowing)

3. Vertebral column (vertebrae and discs)

The Skull

The skull consists of eight sutured bones in the cranium and 13 sutured bones in the face, plus the mandible. The cranium encases the brain and provides attachments for muscles.

Common Types of Fractures

A break in a bone
*CLOSED (simple) fracture - break that does not penetrate the skin
*OPEN (compound) fracture - broken bone penetrated the skin

The Hyoid Bone

The hyoid bone is the only bone that does not articulate with another bone and serves as a moveable base for the tongue.

The Vertebral Column

The vertebral column consists of vertebrae separated by intervertebral discs, forming a curved structure. Each vertebra is named according to its location:
*7 cervical vertebrae
*12 thoracic vertebrae
*5 lumbar vertebrae
*1 sacrum (5 fused)
*1 coccyx (4 fused)
Vertebrae vary in size and morphology.

Joints

Function to give the body flexibility and allow movement to occur.

• Fib