Human Anatomy & Physiology - The Skeleton: Part A
Human Anatomy & Physiology (Ninth Edition) - The Skeleton: Part A
Paranasal Sinuses
Definition: Paranasal sinuses are mucosa-lined, air-filled spaces found within certain cranial bones of the skull. They serve multiple functions and are integral to the anatomy of the nasal cavity.
Functions:
Lighten the skull: The presence of these air-filled spaces reduces the overall weight of the skull, aiding in ease of movement and facilitation of other cranial functions.
Enhance resonance of voice: The sinuses contribute to the quality and tone of the voice by providing a chamber that modifies sound.
Warm and humidify air: The mucosal lining helps in conditioning the air inhaled through the nasal cavity, improving respiratory efficiency.
Location: Found in the following anatomical structures:
Frontal bone
Sphenoid bone
Ethmoid bone
Maxillary bones
Illustrations of Paranasal Sinuses
Figure 7.14a: Frontal sinus, Ethmoidal air cells (sinus), Sphenoidal sinus, Maxillary sinus - Anterior aspect anatomy of paranasal sinuses.
Figure 7.14b: Frontal sinus, Ethmoidal air cells, Sphenoidal sinus, Maxillary sinus - Medial aspect anatomy of paranasal sinuses.
Spatial Relationships in Nasal Anatomy
Figure 32.1: Overview of spatial relationships between the nasal cavity, paranasal sinuses, and nasolacrimal ducts. Includes:
Frontal sinuses
Sphenoidal sinuses
Ethmoidal air cells
Nasolacrimal duct
Maxillary sinuses
Arterial Supply of the Nasal Cavity
Figure 32.7 depicts the arterial supply of the nasal cavity:
Anterior ethmoidal artery
Supplies blood to the anterior region of the nasal cavity.
Posterior ethmoidal artery
Supplies blood to the posterior region of the nasal cavity.
Lateral branches of the sphenopalatine artery
Supply the lateral walls of the nasal cavity.
Other arteries: Include branches supplying the external nasal area and septal regions.
Anatomy of the Skull
Figure 7.5c: Illustrates the bones of the lateral aspect of the skull, including:
Nasal bone
Crista galli
Sella turcica of sphenoid bone
Internal acoustic meatus
Occipital bone and its features: external occipital protuberance, occipitomastoid suture, lambdoid suture
Temporal and parietal bones: depicted along with various cranial sutures
Palatine bone, Vomer, Maxilla: Detailing the various bones forming the structure of the face and skull.
Incisive fossa, Alveolar processes, Mandible: Important structures in dental anatomy and oral cavity.
Vertebral Column Overview
Function: The vertebral column transmits the weight of the trunk to the lower limbs and serves to surround and protect the spinal cord.
Structure: Composed of 26 irregular bones known as vertebrae, categorized into five major regions:
Cervical vertebrae: 7 vertebrae in the neck (C1-C7)
Thoracic vertebrae: 12 vertebrae in the thoracic cage (T1-T12)
Lumbar vertebrae: 5 vertebrae in the lower back (L1-L5)
Sacrum: A single bone inferior to the lumbar vertebrae (made up of fused vertebrae)
Coccyx: The terminus of the vertebral column comprising 4 fused vertebrae.
Curvatures of the Vertebral Column
Definition of Curvatures: Increases resilience and flexibility of the spine, characterized as:
Cervical and lumbar curvatures: Concave posteriorly.
Thoracic and sacral curvatures: Convex posteriorly.
Abnormal Curvatures:
Scoliosis: An abnormal lateral curve.
Kyphosis (hunchback): An exaggerated thoracic curvature.
Lordosis (swayback): An accentuated lumbar curvature.
Figures Illustrating Vertebral Column and Curvatures
Figure 7.16: Diagram of the vertebral column depicting cervical curvature (C1-C7), thoracic curvature (T1-T12), lumbar curvature (L1-L5), sacral curvature, and positions of intervertebral discs.
Figure 7.17: Illustrates abnormal spinal curvatures, including:
(a) Scoliosis
(b) Kyphosis
(c) Lordosis
Developmental Aspects of Spinal Curvature
Primary curvatures: Present at birth, include thoracic and sacral curvatures that give the infant spine a C shape which is convex posteriorly.
Secondary curvatures: Appear as the child develops, becoming more pronounced as the child lifts their head and learns to walk - cervical and lumbar curvatures that become convex anteriorly.
Hyoid Bone
Overview: The hyoid bone is considered not a bone of the skull. It does not articulate directly with other bones but serves critical functions.
Functions:
Acts as a movable base for the tongue.
Serves as an attachment site for muscles involved in swallowing and speech.
Consideration in Forensics: A fractured hyoid bone is often a common finding in cases of strangulation due to its anatomical location and function.
Figures Illustrating the Hyoid Bone
Figure 7.15: Anterior view of the hyoid bone, showing greater horn, lesser horn, and body of the hyoid.
Figure 7.16: Detailed illustration of the hyoid bone in relation to the larynx and stylohyoid muscle, highlighting anatomical relationships relevant in both anatomy and forensic sciences.
Based on the provided notes:
Spinal Curvatures
Developmental Aspects:
Primary curvatures: These are present at birth and include the thoracic and sacral curvatures. They give the infant spine a C shape, which is convex posteriorly.
Secondary curvatures: These appear as a child develops and become more pronounced as the child lifts their head and learns to walk. They include the cervical and lumbar curvatures, which become convex anteriorly.
Abnormal Curvatures:
Scoliosis: An abnormal lateral curve of the spine.
Kyphosis (hunchback): An exaggerated thoracic curvature.
Lordosis (swayback): An accentuated lumbar curvature.
Paranasal Sinuses
Definition: Paranasal sinuses are mucosa-lined, air-filled spaces found within certain cranial bones of the skull.
Locations (or names of the bones they are found in):
Frontal bone (Frontal sinus)
Sphenoid bone (Sphenoidal sinus)
Ethmoid bone (Ethmoidal air cells/sinus)
Maxillary bones (Maxillary sinus)
Functions:
Lighten the skull
Enhance resonance of voice
Warm and humidify air
Human Anatomy & Physiology (Ninth Edition) - The Skeleton: Part A
Paranasal Sinuses
Definition: Paranasal sinuses are mucosa-lined, air-filled spaces found within certain cranial bones of the skull. They serve multiple functions and are integral to the anatomy of the nasal cavity.
Functions:
Lighten the skull: The presence of these air-filled spaces reduces the overall weight of the skull, aiding in ease of movement and facilitation of other cranial functions.
Enhance resonance of voice: The sinuses contribute to the quality and tone of the voice by providing a chamber that modifies sound.
Warm and humidify air: The mucosal lining helps in conditioning the air inhaled through the nasal cavity, improving respiratory efficiency.
Location: Found in the following anatomical structures:
Frontal bone
Sphenoid bone
Ethmoid bone
Maxillary bones
Illustrations of Paranasal Sinuses
Figure 7.14a: Frontal sinus, Ethmoidal air cells (sinus), Sphenoidal sinus, Maxillary sinus - Anterior aspect anatomy of paranasal sinuses.
Figure 7.14b: Frontal sinus, Ethmoidal air cells, Sphenoidal sinus, Maxillary sinus - Medial aspect anatomy of paranasal sinuses.
Spatial Relationships in Nasal Anatomy
Figure 32.1: Overview of spatial relationships between the nasal cavity, paranasal sinuses, and nasolacrimal ducts. Includes:
Frontal sinuses
Sphenoidal sinuses
Ethmoidal air cells
Nasolacrimal duct
Maxillary sinuses
Arterial Supply of the Nasal Cavity
Figure 32.7 depicts the arterial supply of the nasal cavity:
Anterior ethmoidal artery
Supplies blood to the anterior region of the nasal cavity.
Posterior ethmoidal artery
Supplies blood to the posterior region of the nasal cavity.
Lateral branches of the sphenopalatine artery
Supply the lateral walls of the nasal cavity.
Other arteries: Include branches supplying the external nasal area and septal regions.
Anatomy of the Skull
Figure 7.5c: Illustrates the bones of the lateral aspect of the skull, including:
Nasal bone
Crista galli
Sella turcica of sphenoid bone
Internal acoustic meatus
Occipital bone and its features: external occipital protuberance, occipitomastoid suture, lambdoid suture
Temporal and parietal bones: depicted along with various cranial sutures
Palatine bone, Vomer, Maxilla: Detailing the various bones forming the structure of the face and skull.
Incisive fossa, Alveolar processes, Mandible: Important structures in dental anatomy and oral cavity.
Vertebral Column Overview
Function: The vertebral column transmits the weight of the trunk to the lower limbs and serves to surround and protect the spinal cord.
Structure: Composed of 26 irregular bones known as vertebrae, categorized into five major regions:
Cervical vertebrae: 7 vertebrae in the neck (C1-C7)
Thoracic vertebrae: 12 vertebrae in the thoracic cage (T1-T12)
Lumbar vertebrae: 5 vertebrae in the lower back (L1-L5)
Sacrum: A single bone inferior to the lumbar vertebrae (made up of fused vertebrae)
Coccyx: The terminus of the vertebral column comprising 4 fused vertebrae.
Curvatures of the Vertebral Column
Definition of Curvatures: Increases resilience and flexibility of the spine, characterized as:
Cervical and lumbar curvatures: Concave posteriorly.
Thoracic and sacral curvatures: Convex posteriorly.
Abnormal Curvatures:
Scoliosis: An abnormal lateral curve.
Kyphosis (hunchback): An exaggerated thoracic curvature.
Lordosis (swayback): An accentuated lumbar curvature.
Figures Illustrating Vertebral Column and Curvatures
Figure 7.16: Diagram of the vertebral column depicting cervical curvature (C1-C7), thoracic curvature (T1-T12), lumbar curvature (L1-L5), sacral curvature, and positions of intervertebral discs.
Figure 7.17: Illustrates abnormal spinal curvatures, including:
(a) Scoliosis
(b) Kyphosis
(c) Lordosis
Developmental Aspects of Spinal Curvature
Primary curvatures: Present at birth, include thoracic and sacral curvatures that give the infant spine a C shape which is convex posteriorly.
Secondary curvatures: Appear as the child develops, becoming more pronounced as the child lifts their head and learns to walk - cervical and lumbar curvatures that become convex anteriorly.
Hyoid Bone
Overview: The hyoid bone is considered not a bone of the skull. It does not articulate directly with other bones but serves critical functions.
Functions:
Acts as a movable base for the tongue.
Serves as an attachment site for muscles involved in swallowing and speech.
Consideration in Forensics: A fractured hyoid bone is often a common finding in cases of strangulation due to its anatomical location and function.
Figures Illustrating the Hyoid Bone
Figure 7.15: Anterior view of the hyoid bone, showing greater horn, lesser horn, and body of the hyoid.
Figure 7.16: Detailed illustration of the hyoid bone in relation to the larynx and stylohyoid muscle, highlighting anatomical relationships relevant in both anatomy and forensic sciences.
Spinal Curvatures
Developmental Aspects:
Primary curvatures: These are present at birth and include the thoracic and sacral curvatures. They give the infant spine a C shape, which is convex posteriorly.
Secondary curvatures: These appear as a child develops and become more pronounced as the child lifts their head and learns to walk. They include the cervical and lumbar curvatures, which become convex anteriorly.
Abnormal Curvatures:
Scoliosis: An abnormal lateral curve of the spine.
Kyphosis (hunchback): An exaggerated thoracic curvature.
Lordosis (swayback): An accentuated lumbar curvature.
Paranasal Sinuses
Definition: Paranasal sinuses are mucosa-lined, air-filled spaces found within certain cranial bones of the skull.
Locations (or names of the bones they are found in):
Frontal bone (Frontal sinus)
Sphenoid bone (Sphenoidal sinus)
Ethmoid bone (Ethmoidal air cells/sinus)
Maxillary bones (Maxillary sinus)
Functions:
Lighten the skull
Enhance resonance of voice
Warm and humidify air
Cartilage Types and Locations
Hyaline Cartilage:
Locations: Articular cartilages (covering ends of most bones at movable joints), costal cartilages (connecting ribs to sternum), respiratory cartilages (forming larynx, reinforcing other respiratory passageways), nasal cartilages (supporting the external nose).
Elastic Cartilage:
Locations: External ear (pinna), epiglottis (covering the opening of the larynx).
Fibrocartilage:
Locations: Menisci of the knee, intervertebral discs, pubic symphysis.
Classification of Bones
Bones are classified into four main categories based on their shape:
Long Bones:
Description: Considerably longer than they are wide. Generally consist of a shaft with heads at both ends.
Examples: Humerus, femur, tibia, fibula, ulna, radius, phalanges.
Short Bones:
Description: Roughly cube-shaped. More or less equal in length, width, and thickness.
Examples: Carpals (wrist bones), tarsals (ankle bones).
Flat Bones:
Description: Thin, flattened, and usually a bit curved. They have two roughly parallel compact bone surfaces sandwiching a layer of spongy bone.
Examples: Sternum, scapulae, ribs, most skull bones.
Irregular Bones:
Description: Bones that have complicated shapes and do not fit into the other categories.
Examples: Vertebrae, hip bones.
Functions of Bones
Bones perform various critical functions in the body:
Support: Provide a framework for the body and cradle soft organs.
Protection: Protect delicate internal organs (e.g., skull protects brain, rib cage protects heart and lungs).
Movement: Act as levers for muscles to pull on, allowing for movement.
Mineral and Growth Factor Storage: Store minerals, especially calcium (Ca^{2+}) and phosphate, and release them into the blood as needed. Also store growth factors.
Blood Cell Formation (Hematopoiesis): Occurs in the red bone marrow of certain bones.
Triglyceride (Fat) Storage: Yellow bone marrow in bone cavities is a source of stored energy.
Hormone Production: Osteocalcin, a hormone produced by bones, helps regulate insulin secretion, glucose homeostasis, and energy expenditure.
Structure of Compact Bone and Spongy Bone
Compact Bone:
Structure: Dense outer layer that looks smooth and solid. It is organized into structural units called osteons (Haversian systems).
Function: Resists stresses applied to the bone.
Spongy Bone (Cancellous Bone):
Structure: Consists of trabeculae (needle-like or flat pieces of bone) that form an open network, leaving open spaces filled with red or yellow bone marrow. Trabeculae are precisely aligned to resist stress.
Function: Supports shifts in weight distribution, houses bone marrow.
Structure of Long and Flat Bones
Long Bones:
Diaphysis: The shaft, forming the long axis of the bone. Composed of compact bone surrounding a medullary (marrow) cavity.
Epiphyses: The bone ends (proximal and distal). Consist of compact bone externally and spongy bone internally. Joint surface is covered with articular (hyaline) cartilage.
Metaphysis: The region where the diaphysis and epiphysis meet. In growing bones, it contains the epiphyseal plate.
Periosteum: A white, double-layered membrane covering the external surface of the entire bone except for the joint surfaces. It has an outer fibrous layer (dense irregular connective tissue) and an inner osteogenic layer containing osteogenic cells.
Endosteum: A delicate connective tissue membrane covering internal bone surfaces (medullary cavity, trabeculae of spongy bone). Contains osteogenic cells.
Articular Cartilage: Hyaline cartilage covering the joint surfaces of epiphyses, cushioning the bone ends and absorbing stress.
Epiphyseal Plate (Growth Plate): A disc of hyaline cartilage that grows during childhood to lengthen the bone. In adults, it is replaced by the epiphyseal line.
Flat Bones:
Structure: Consist of two layers of compact bone with a layer of spongy bone (diploe) in between. There is no diaphysis or epiphyses.
Periosteum and Endosteum: Covered externally by periosteum and internally by endosteum.
Marrow: Bone marrow is found within the diploe.
Bone Marrow
Red Bone Marrow:
Definition: Hematopoietic tissue responsible for producing blood cells (red blood cells, white blood cells, platelets).
Location: In adults, primarily found in the spongy bone of the axial skeleton, girdles, and proximal epiphyses of the humerus and femur. In infants, found in the medullary cavity of long bones and all spongy bone.
Yellow Bone Marrow:
Definition: Adipose tissue (fat) storage.
Location: Found in the medullary cavity of long bones in adults (stores triglycerides). Can convert to red marrow if needed (e.g., severe anemia).
Cells of the Bone
Osteogenic Cells (Osteoprogenitor Cells):
Function: Mitotically active stem cells found in the periosteum and endosteum. They differentiate into osteoblasts or bone-lining cells.
Osteoblasts:
Function: Bone-forming cells. Secrete the bone matrix (osteoid). When active, they are cuboidal or pyramidal. They become osteocytes when they are trapped in the matrix they've secreted.
Osteocytes:
Function: Mature bone cells. Occupy lacunae in the bone matrix. They monitor and maintain the bone matrix, act as stress or strain sensors, and communicate with osteoblasts and osteoclasts to trigger bone remodeling.
Bone-Lining Cells:
Function: Flat cells found on bone surfaces where bone remodeling is not occurring. They help maintain the matrix.
Types: Periosteal cells (on external bone surface), Endosteal cells (on internal bone surface).
Osteoclasts:
Function: Giant, multinucleate cells derived from hematopoietic stem cells that resorb (break down) bone matrix. They have ruffled borders that increase surface area for enzymatic degradation of bone.
Structure of the Osteon (Haversian System)
An osteon is the structural unit of compact bone, a tiny weight-bearing pillar.
Central (Haversian) Canal: Runs through the core of each osteon, containing small blood vessels and nerve fibers.
Perforating (Volkmann's) Canals: Lie at right angles to the long axis of the bone, connecting the blood and nerve supply of the periosteum to those in the central canals and medullary cavity.
Lamellae: Concentric rings of bone matrix running in different directions, forming a series of hollow tubes within an osteon. They resist twisting stresses.
Lacunae: Small cavities or "lakes" at the junctions of the lamellae, housing osteocytes.
Canaliculi: Hairlike canals that connect lacunae to each other and to the central canal, allowing osteocytes to communicate and exchange nutrients and wastes.
Composition of Bone
Bone matrix is composed of both organic and inorganic components.
Organic Components (Osteoid):
Composition: Accounts for approximately one-third of the bone matrix. Includes ground substance (proteoglycans and glycoproteins) and collagen fibers (primarily type I).
Function: Contributes to bone's flexibility and tensile strength, allowing it to resist stretching and twisting.
Inorganic Components (Mineral Salts):
Composition: Consists mainly of hydroxyapatites (mineral salts), largely calcium phosphates, present as tiny, tightly packed crystals between collagen fibers.
Function: Accounts for bone's hardness and ability to resist compression.
Endochondral Ossification
Type of Bone it Occurs in: Forms most bones inferior to the base of the skull, except for the clavicles. This process uses a hyaline cartilage model as a template for bone formation.
Main Steps of the Process:
Step 1: Bone collar forms around the diaphysis of the hyaline cartilage model. Osteoblasts in the periosteum secrete osteoid against the cartilage model.
Step 2: Cartilage calcifies in the center of the diaphysis and then develops cavities. Chondrocytes enlarge, calcify the surrounding matrix, and die, causing the matrix to deteriorate.
Step 3: The periosteal bud invades the internal cavities and spongy bone forms. The periosteal bud (containing an artery, vein, nerve, red marrow elements, osteogenic cells, and osteoclasts) enters the cavities. Osteoclasts erode calcified cartilage, and osteoblasts secrete osteoid.
Step 4: The diaphysis elongates and a medullary cavity forms. Cartilage forms at the epiphyseal faces, and the ossification front follows. Osteoclasts break down newly formed spongy bone to open up the medullary cavity.
Step 5: The epiphyses ossify. Secondary ossification centers appear in the epiphyses (usually around birth). Cartilage remains only in the epiphyseal plates and articular cartilages.
Primary Ossification Center: The first area of bone development, located in the center of the diaphysis, where bone formation begins.
Secondary Ossification Centers: Areas of bone development that appear in the epiphyses, typically after birth.
Intramembranous Ossification
Type of Bone it Occurs in: Forms the cranial bones of the skull (frontal, parietal, occipital, temporal) and the clavicles. This process forms bone directly from fibrous connective tissue membranes.
Main Steps of the Process:
Step 1: Ossification centers appear in the fibrous connective tissue membrane. Mesenchymal cells cluster and differentiate into osteoblasts.
Step 2: Osteoid is secreted within the fibrous membrane and then calcifies. Osteoblasts secrete osteoid, which then calcifies within a few days. Trapped osteoblasts become osteocytes.
Step 3: Woven bone and periosteum form. Accumulating osteoid is laid down between embryonic blood vessels in a random manner, forming trabeculae of woven bone. Vascularized mesenchyme condenses on the external surface of the woven bone and becomes the periosteum.
Step 4: Lamellar bone replaces woven bone, and red marrow appears. Trabeculae just deep to the periosteum thicken. Woven bone is replaced by mature lamellar bone, and spongy bone (diploe) consisting of distinct trabeculae fills the interior. Red marrow develops in the spongy bone.
Bone Growth
Growth in Length (Longitudinal Growth):
Occurs at the epiphyseal plate (growth plate) via endochondral ossification.
Cartilage cells proliferate on the epiphyseal side, pushing the epiphysis away from the diaphysis.
Cartilage cells on the diaphyseal side hypertrophy, calcify, die, and are replaced by bone, lengthening the diaphysis.
This process continues until the epiphyseal plate closes, becoming the epiphyseal line, typically in late adolescence or early adulthood.
Growth in Width (Appositional Growth):
Occurs throughout life.
Osteoblasts beneath the periosteum secrete bone matrix on the external bone surface.
Osteoclasts on the endosteal surface of the diaphysis remove bone, widening the medullary cavity.
This results in thicker, stronger bone without excessive increases in weight.
Bone Remodeling
Bone remodeling is a continuous process of bone deposition and bone resorption that occurs throughout life.
Mechanism: Orchestrated by genetic factors and two control loops: hormonal controls (maintaining blood Ca^{2+} homeostasis) and mechanical and gravitational forces (Wolff's Law).
Cells Involved:
Bone Deposition: Primarily carried out by osteoblasts, which secrete osteoid (bone matrix) that then calcifies.
Bone Resorption: Primarily carried out by osteoclasts, which break down bone matrix by secreting lysosomal enzymes and acids.
Calcium Homeostasis
Maintaining stable blood calcium levels (9-11 mg/dL) is crucial.
Parathyroid Hormone (PTH):
Influence: Primary hormone regulating blood Ca^{2+} levels when they are too low.
Mechanism: Released by the parathyroid glands when Ca^{2+} levels drop. PTH stimulates osteoclasts to resorb bone, releasing Ca^{2+} into the bloodstream. It also enhances Ca^{2+} reabsorption in the kidneys and activates vitamin D, which promotes Ca^{2+} absorption in the intestine.
Calcitonin:
Influence: Hormone that may play a minor role in regulating blood Ca^{2+} levels, especially when they are high (though its effects in adults are less significant than PTH).
Mechanism: Produced by parafollicular cells of the thyroid gland. Calcitonin lowers blood Ca^{2+} levels by inhibiting osteoclast activity and stimulating Ca^{2+} uptake by the bone matrix.
Wolff's Law
Wolff's Law: States that a bone grows or remodels in response to the demands placed on it. This means that if stresses are applied to a bone, it will thicken and strengthen over time to withstand those stresses. Conversely, if mechanical stresses are removed, the bone will thin and weaken. This explains why bone abnormalities are common in astronauts (due to lack of gravity) and why people who exercise regularly have stronger bones.
Fracture Classification
Fractures are breaks in the bone and can be classified in several ways:
Position of bone ends after fracture: Nondisplaced (ends retain normal position) or displaced (ends are out of normal alignment).
Completeness of the break: Complete (bone is broken through) or incomplete (bone is not broken through).
Orientation of the break to the long axis of the bone: Linear (parallel to the long axis) or transverse (perpendicular to the long axis).
Whether the bone ends penetrate the skin: Open (compound, skin is penetrated) or closed (simple, skin is not penetrated).
Common Fracture Types:
Comminuted: Bone fragments into three or more pieces. Common in older people whose bones are more brittle.
Compression: Bone is crushed. Common in porous bones (e.g., osteoporotic bones) subjected to extreme trauma.
Spiral: Ragged break occurs when excessive twisting forces are applied to a bone. Common sports fracture.
Epiphyseal: Epiphysis separates from the diaphysis along the epiphyseal plate. Tends to occur where cartilage cells are dying and calcification of the matrix is occurring.
Depressed: Broken bone portion is pressed inward. Typical of skull fracture.
Greenstick: Bone breaks incompletely, much in the way a green twig breaks. Only one side of the shaft breaks; the other side bends. Common in children, whose bones are more flexible.
Bone Disorders
Osteomalacia (Adult Rickets):
Definition: A disorder in adults where bones are inadequately mineralized, leading to soft, weak bones. The osteoid is produced, but calcium salts are not deposited effectively.
Causes: Insufficient calcium in the diet or vitamin D deficiency.
Rickets (Childhood Osteomalacia):
Definition: The analogous condition in children. Because young bones are still growing, rickets manifests as bowed legs and deformities of the pelvis, skull, and rib cage.
Causes: Insufficient calcium in the diet or vitamin D deficiency.
Differences between Osteomalacia and Osteoporosis:
Osteomalacia: Problem with bone mineralization. Bone matrix (osteoid) is present, but it's not hardened with calcium, leading to soft bones.
Osteoporosis: Problem with bone mass. Both organic and inorganic components of the bone matrix are lost, leading to porous, fragile bones that are prone to fracture.
Osteoporosis:
Definition: A group of diseases in which bone resorption outpaces bone deposition, making the bones porous and lighter, predisposing them to fractures.
Risk Factors:
Age: Bone density naturally declines with age.
Gender: Postmenopausal women are at higher risk due to declining estrogen levels, which normally inhibits osteoclast activity.
Heredity: Genetic predisposition.
Nutritional factors: Insufficient calcium and vitamin D intake.
Lifestyle factors: Sedentary lifestyle, smoking, excessive alcohol consumption.
Medical conditions: Certain diseases (e.g., hyperthyroidism, diabetes mellitus) and medications (e.g., corticosteroids).
Treatment:
Calcium and Vitamin D supplements: To ensure adequate mineral availability.
Weight-bearing exercise: To stimulate bone deposition.
Bisphosphonates: Drugs that decrease osteoclast activity.
Selective Estrogen Receptor Modulators (SERMs): Mimic estrogen's beneficial effects on bone without affecting other estrogen-sensitive tissues.
Denosumab: Monoclonal antibody that inhibits osteoclast formation and function.
Teriparatide (PTH analog): Stimulates new bone formation if used intermittently.
Paget's Disease:
Definition: A chronic disease of bone characterized by excessive and haphazard bone deposit and resorption. This results in a high ratio of spongy to compact bone and reduced mineralization, leading to bone deformities and weakened, enlarged bones.
Causes: Unknown, but may involve a virus. A genetic component is also suspected.
Symptoms: Vary depending on the bone affected. Can include bone pain, deformities, and fractures. Typically localized to specific bones (e.g., pelvis, skull, spine, femur, tibia).