Week 4 - Physiology (Skeleton & Joints) PDF

**[Week 4 - Physiology (Skeleton & Joints)]** [Objectives:] \- Identify the functions of the skeletal system. \- Describe the structure and functions of each part of a long bone. \- Identify common types of fractures and the process of fracture repair. \- Identify the major joints of the body b...

**[Week 4 - Physiology (Skeleton & Joints)]** [Objectives:] \- Identify the functions of the skeletal system. \- Describe the structure and functions of each part of a long bone. \- Identify common types of fractures and the process of fracture repair. \- Identify the major joints of the body by location, classification, and movements. \- Identify the structural and functional classifications of joints. \- Describe the types of movements that can occur at synovial joints. [Functions of skeletal system:] \- Bone, an organ works along with related cartilage, connective tissue, epithelium, adipose tissue, blood and nervous tissue. \- Entire framework of bones and cartilages makes up skeletal system \- Study of bones and disorders is osteology. \- Several functions of skeletal system are: **a) Support** **b) Protection** **c) Movement** **d) Mineral Homeostasis** **e) Blood Cell Production** -- Hematopoiesis **f) Fat Storage** -- Triglycerides in yellow bone marrow [Structure of a Bone:] A long bone consists of: **1. Epiphyses** -- proximal & distal ends of the long bone **2. Diaphysis** -- body or shaft **3. Metaphyses** -- region between epiphyses & diaphysis. Has epiphyseal growth plate (layer of hyaline cartilage), which allows diaphysis to grow long. Around age 24, this plate is replaced by bone and appears as an epiphyseal line. **4. Articular cartilage** -- thin layer of hyaline cartilage covering epiphysis. Lacks perichondrium (dense connective tissue) & blood vessels hence repair is limited. **5. Periosteum** -- outermost covering (connective tissue) of bone. Has outer fibrous layer and inner osteogenic layer that consists of osteoprogenitor cells. **6. Medullary cavity** -- marrow cavity within diaphysis has both red and yellow marrow. Bone weight is reduced by this hollow cavity. **7. Endosteum** -- thin connective tissue (membrane) lining the medullary cavity and internal spaces of spongy bone. Has osteoprogenitor cells. \- Microscopically, 55% of a bone is mineral salt (predominantly, calcium phosphate). \- **Calcification** (hardening of the bone) is the formation of crystals (hydroxyapatite) around collagen fibers when calcium phosphate reacts with calcium hydroxide. There are 4 different kinds of cells present in bone tissue: **1. Osteoprogenitor cells** -- undifferentiated stem cells which give rise to other cell types. Only cells possess mitosis capability. **2. Osteoblasts** -- bone-building cells. Secretes extracellular matrix (collagen etc.) by a process called bone deposition and then initiates calcification. **3. Osteocytes** -- mature cells that maintain bone metabolism. **4. Osteoclasts** -- breaks down bone for bone resorption. chew or carve. [Bone classification: ] \- Compact (dense) bone -- has few spaces (trabeculae). Provides protection & support. \- Osteons (Haversian systems) -- repeating units; each unit has concentric bone lamellae arranged around the osteonic (haversian or central) canal. \- Spaces between lamellae are bone lacunae, which have osteocytes. \- Bone canaliculi - small channels radiate from bone lacunae (has ECF). \- Areas between neighboring osteons containing bone lamellae are interstitial bone lamellae. \- Vessels & nerves penetrate periosteum through openings - perforating (Volkmann's) canals. \- Circumferential bone lamellae close to the periosteum is external circumferential bone lamellae while the one covering the medullary cavity is called internal circumferential bone lamellae. \- Spongy (Trabecular) bone -- or cancellous bone. Does NOT have osteons. Spongy bone is always covered by compact bone. Bone lamellae are arranged in irregular columns called bone trabeculae which contain osteocytes. This bone is lighter than compact bone and helps to protect red bone marrow. [Types of bones:] \- A total of 206 bones are present in adults. Infants & children have more because many bones are not completely fused yet. \- These bones can be grouped based on their shape, location and structure into 6 types: **1. Sutural bones** -- based on location e.g. small bones forming sutural joints of the skull. **2. Irregular bones** -- have complicated shapes usually based on specialized functions such as vertebrae, mandibles etc. **3. Short bones** -- have equal length & width, e.g. carpal & tarsal bones in the hand & feet respectively. **4. Flat bones** -- thin & flat, provides larger surface area for muscles/tendons/ligaments. Eg., scapula, pelvis, sternum. **5. Long bones** -- have length greater than width. Eg., femur, humerus. **6. Sesamoid bones** -- small bones embedded in tendons generally in areas of high friction, tension (physical stress) eg., patella [Joints:] Joint is a site where two skeletal elements come together. General categories are: **1. Synovial joints** -- skeletal elements (bones) are separated by a cavity **2. Solid joints** -- there is no cavity & bones are held by a connective tissue [Synovial Joints:] **-** The joint cavity is also known as **articular cavity** and possesses the joint -- a site where two skeletal elements come together. **-** **Articular cartilage** is a specialized form of hyaline cartilage. It is smooth, resilient, and provides a low-friction surface for the bones in the joint to glide over each other during movement. **- Avascular and Aneural:** Like other types of cartilage, articular cartilage is avascular (lacks blood vessels) and aneural (lacks nerve supply). This means it relies on the diffusion of nutrients from the synovial fluid within the joint for maintenance and repair. **- Collagen Fibers:** The extracellular matrix of articular cartilage is rich in type II collagen fibers, which provide tensile strength and help maintain the structural integrity of the cartilage. **- Proteoglycans:** These are molecules that attract water, giving the cartilage its gel-like consistency and helping it resist compressive forces. **- Joint capsule** -- has inner synovial and outer fibrous membrane. Synovial membrane attaches to the margins of the joint surfaces at the interface between cartilage & bone & encloses the articular cavity. Highly vascular producing synovial fluid that lubricates & nourishes the joint. **- Synovial bursae** or **tendon sheaths** are closed sacs of synovial membrane extending outside the joint. Bursae reduces friction between tendons & bones, tendons & joints, skin & bone. While tendon sheath surrounds tendons to reduce friction. [Synovial Joints - Classification:] \- Based on movement, synovial joints are classified as: **1. Uniaxial** -- movement is limited across one plane. Eg. Elbow, knee, ankle **2. Biaxial** -- movement is limited to two planes. Eg. Metacarpophalangeal joint (knuckle joint) **3. Multi-axial** -- Movement across multiple directions/planes. Eg. Shoulder, hip joint. \- Based on the shape of their articular surface, synovial joints are classified as **Plane (flat)** -- allowing sliding/gliding movements. Eg. Acromioclavicular joint (acromion of scapula & clavicle bone) **- Hinge joint** -- or **Ginglymus joint** allows movement across one axis that is transverse to the joint. Eg. elbow joint, knee joint, interphalangeal joints, etc. **- Pivot joint** -- joint allows movement across one axis that is longitudinal to the joint. Eg. Atlantoaxial joint (atlas & axis vertebra) **- Condylar joint** -- or ellipsoid joint allows movement around two axes that are at right angles to each other. An elliptical convex articular surface fits into an elliptical concave articular surface. Biaxial movements are allowed. E.g. Wrist -- flexion/extension and abduction/adduction **- Saddle joint** -- allows movement around two axes that are at right angles to each other. E.g. Trapeziometacarpal joint (carpal-metacarpal joint of the thumb) **- Ball-and-socket joint** (or **Spheroid joint**) -- allows movement around multiple axes. Eg. hip joint, shoulder joint (glenohumeral) [Solid Joints:] Two skeletal elements are connected by a strong fibrous connective tissue or by cartilage (usually fibrocartilage). Movements are more restricted than a synovial joint. Fibrous joints: **- Sutures** -- occurs in the skull connected by fibrous connective tissue called sutural ligament **- Gomphoses** -- occurs between teeth & mandible or maxilla. Short collagen tissue fibers run between the tooth & the bony socket. **- Syndesmoses** -- two adjacent bones are linked by a ligament. Eg., interosseous membrane connecting radius and ulna in antebrachium Cartilaginous joints: **- Synchondroses** -- two ossification centers remain separated by a layer of cartilage during bone development. Eg., epiphysis and diaphysis of a long bone **- Symphyses** -- Two separate bones are interconnected by cartilage. Eg., pubic symphysis (pelvis), intervertebral discs [Basic movements:] These are the basic movements: **1. Flexion & Extension** -- Decreasing & increasing the angle at the joint, respectively. **2. Dorsiflexion & Plantar flexion** -- Applies to the foot. **3. Eversion & Inversion** -- Complex movements involving multiple planes. Eg., occurring at the level of intertarsal joints (not ankle). **a) Inversion** is the turning of the foot towards midline (the plantar surface will face midline). **b) Eversion** is the turning of bottom away from the midline (plantar surface faces away from midline). **4. Pronation & Supination** -- movements of the forearm (antebrachium). **a) Supination** is the palmar surface facing forward or upwards (like asking for soup in the form of a gesture). **b)** When the palm of the hand faces backward, the forearm is in the **pronated** position. Radius & ulna will form an X-shape. **5. Abduction & Adduction** -- medial or lateral movement from the body. **a) Abduction** moves the limb laterally away from the centreline while **adduction** is the opposite movement. **b)** These movements are seen in condyloid, saddle & ball & socket joints. **6. Rotation** -- Rotation of body, neck, arms can occur either laterally or medially. Rotation of the body doesn't specify medial or lateral. **7. Circumduction** -- circular movement wherein one end stays stationary relative to the other rotating end. **8. Elevation & Depression** -- upward & downward movement respectively. Applicable to scapula, mandible movements. **9. Excursion** -- Side to side movement of the mandible. Lateral excursion moves the mandible away from the midline (left or right side). Medial excursion returns the mandible to the medial position (resting position at the midline). **a) Protraction & Retraction** -- anterior & posterior movements of the scapula, mandible. **10. Opposition & Reposition** -- thumb movement that brings the tip of the thumb in contact with the tip of a finger. Occurs at the level of carpometacarpal joint. [Selected Axial Skeleton Joints:] **- Suture:** The articular components are between skull bones... The classification is fibrous... And it has no movements. **- Atlanto-Occipital:** The articular components are between superior articular facets of atlas and occipital condyles of occipital bone... The classification is Synovial (ellipsoid)\... The movements are Flexion and extension of head; slight lateral flexion of head to either side. **- Atlanto-Axial:** The articular components are 1) Between dens of axis and anterior arch of atlas; And 2) Between lateral masses of atlas and axis... The classification is Synovial (pivot) between dens and anterior arch; synovial (planar) between lateral masses... And the movement is rotation of the head. **- Intervertebral:** The articular components are 1) Between vertebral bodies; And 2) Between vertebral arches... The classification is cartilaginous (symphysis) between vertebral bodies; synovial (planar) between vertebral arches... And the movements are flexion, extension, lateral flexion, and rotation of the vertebral column. **- Vertebrocostal:** The articular components are 1) Between articular facets of heads of ribs and costal facets of bodies of adjacent thoracic vertebrae and intervertebral discs between them; And 2) Between the articular facet of the tubercles of the ribs and the transverse costal facet of the thoracic... The classification is Synovial (planar)\... And the movement is slightly gliding. **- Sternocostal:** The articular components are between the sternum and first seven pairs of ribs... The classification is cartilaginous (synchondrosis) between sternum and first pair of ribs; synovial (plane) between sternum and second through seventh pairs of ribs... And the movements are none between sternum and first pair of ribs; slight gliding between sternum and second through seventh pairs of ribs. **- Lumbosacral:** The articular components are 1) Between body of fifth lumbar vertebra and base of sacrum; And 2) Between inferior articular facets of the fifth lumbar vertebra and superior articular facets of the first vertebra of sacrum... The classification is Cartilaginous (symphysis) between body and base; synovial (planar) between articular facets... And the movements are Flexion, extension, lateral flexion, and rotation of the vertebral column. **- Sternoclavicular:** The articular components are between the sternal end of the clavicle, manubrium of sternum, and first costal cartilage... The classification is Synovial (plane, pivot)\... And the movements are Gliding, with limited movements in nearly every direction. **- Acromioclavicular:** The articular components are Between acromion of the scapula and the acromial end of the clavicle... The classification is Synovial (plane)\... And the movements are Gliding and rotation of the scapula on the clavicle. **- Radioulnar:** The articular components are the proximal radioulnar joint between head of radius and radial notch of ulna; distal radioulnar joint between ulnar notch of radius and head of ulna... The classification is Synovial (pivot)\... And the movements are Rotation of the forearm. **- Wrist (radiocarpal):** The articular components are Between distal end of radius and scaphoid, lunate, and triquetrum of carpus... The classification is Synovial (ellipsoid)\... And the movements are Flexion, extension, abduction, adduction, circumduction, and slight hyperextension of wrist. **- Intercarpal:** The articular components are Between proximal row of carpal bones, distal row of carpal bones, and between both rows of carpal bones (midcarpal joints)\... The classification is Synovial (plane), except for hamate, scaphoid, and lunate (midcarpal) joint, which is synovial (saddle)\... And the movements are Gliding plus flexion, extension, abduction, adduction, and slight rotation at midcarpal joints. **- Carpometacarpal:** The articular components are Carpometacarpal joint of thumb between trapezium of carpus and first metacarpal; carpometacarpal joints of remaining digits formed between carpus and second through fifth metacarpals... The classification is Synovial (saddle) at thumb; synovial (plane) at remaining digits... And the movements are Flexion, extension, abduction, adduction, and circumduction at thumb; gliding at remaining digits. **- Metacarpophalangeal & Metatarsophalangeal:** The articular components are Between heads of metacarpals (or metatarsals) and bases of proximal phalanges... The classification is Synovial (ellipsoid)\... And the movements are Flexion, extension, abduction, adduction, and circumduction of phalanges. **- Interphalangeal:** The articular components are Between heads of phalanges and bases of more distal phalanges... The classification is Synovial (hinge)\... And the movements are Flexion and extension of phalanges. **- Sacroiliac:** The articular components are Between auricular surfaces of sacrum and ilia of hip bones... The classification is Synovial (plane)\... And the movement is Slight gliding (even more so during pregnancy). **- Pubic symphysis:** The articular components are Between anterior surfaces of hip bones... The classification is Cartilaginous (symphysis)\... and the movements are Slight movements (even more so during pregnancy). **- Tibiofibular:** The articular components are proximal tibiofibular joint between lateral condyle of tibia and head of fibula; distal tibiofibular joint between distal end of fibula and fibular notch of tibia... The classification is Synovial (plane) at proximal joint; fibrous (syndesmosis) at distal joint... and the movements are Slight gliding at proximal joint; slight rotation of fibula during dorsiflexion of foot. **- Ankle (Talocrural):** The articular components are 1) Between distal end of tibia and its medial malleolus and talus; And 2) Between lateral malleolus of fibula and talus... The classification is Synovial (hinge)\... and the movements are Dorsiflexion and plantar flexion of foot. **- Intertarsal:** The articular components are Subtalar joint between talus and calcaneus of tarsus; talocalcaneonavicular joint between talus and calcaneus and navicular of tarsus; calcaneocuboid joint between calcaneus and cuboid of tarsus... The classifications are Synovial (plane) at subtalar and calcaneocuboid joints; synovial (saddle) at talocalcaneonavicular joint... And the movements are Inversion and eversion of foot. **- Tarsometatarsal:** The articular components are Between three cuneiforms of tarsus and bases of five metatarsal bones... The classification is Synovial (plane)\... And the movement is Slight gliding. [Temporomandibular Joint: ] **Anatomical Components:** \- Articular capsule. \- Articular disc (meniscus), Lateral ligament, Sphenomandibular ligament, Stylomandibular ligament. **Movements:** \- Depression, elevation, protraction, retraction, lateral displacement, slight rotation. [Shoulder Joint:] **Anatomical Components:** \- Articular capsule. \- Coracohumeral ligament, Glenohumeral ligaments, Transverse humeral ligament, Glenoid labrum, Bursae. **Movements:** \- Flexion, extension, hyperextension, abduction, adduction, medial and lateral rotation, circumduction. [Glenohumeral Joint Injuries: ] **- Rotator cuff injury** -- occurs from wear and tear, aging, trauma, poor posture, improper lifting and repetitive movements. **- Dislocated shoulder** -- head of humerus becomes displaced from glenoid cavity; damages ligaments, tendons, muscles. **- Separated shoulder** -- partial or complete tearing of acromioclavicular ligament [Elbow Joint: ] **Anatomical Components:** \- Articular capsule. \- Ulnar collateral ligament, Radial collateral ligament, Annular ligament of the radius. **Movements:** \- Flexion and extension. [Elbow Joint Injuries: ] **- Tennis Elbow** -- pain at or near lateral epicondyle of humerus. **- Little League Elbow** -- inflammation of the medial epicondyle. **- Dislocation of the radial head** -- most common upper limb dislocation in children. Head of radius slides past radial annular ligament. [Hip Joint: ] **Anatomical Components** \- Articular capsule \- Iliofemoral ligament, Pubofemoral ligament, Ischiofemoral ligament, Ligament of the head of the femur, Acetabular labrum, Transverse acetabular ligament. **Movements:** \- Flexion, extension, abduction, adduction, medial and lateral rotation, circumduction. [Knee Joint:] **Anatomical Components:** \- Articular capsule \- Medial and Lateral patellar retinaculum, Patellotibial ligament, Oblique popliteal ligament, Arcuate popliteal ligament, Tibial collateral ligament, Fibular collateral ligament, intracapsular ligaments (ACL and PCL), Articular discs, Bursae. **Movements:** \- Flexion, extension, slight medial and lateral rotation. [Aging and Joints:] As we age, our joints experience: \- Decreased production of synovial fluid \- Thinning of articular cartilage \- Loss of ligament length and flexibility \- Arthroplasty \- Joint replacement surgery can be performed to counter some of the effects of aging [Fracture: ] A break in the bone is referred to as a fracture. It can occur microscopically or grossly. Microscopic fractures are called stress fractures. Broadly, fractures can be classified as follows: **- Open fracture** -- breakage of bone includes disruption in skin (visibly wound on the skin). High risk of infection to the bone (osteomyelitis). Also called a **compound fracture.** **- Closed fracture** -- skin stays intact. No puncture or open wound. **- Displaced fracture** -- bone breaks into two or more pieces, & gets misaligned. Comminuted is 3 or more pieces. **- Non-Displaced fracture** -- bone breaks into parts but alignment is maintained. The following are some subtypes of fracture: **- Transverse fracture** -- fracture line is perpendicular to the shaft of the bone. **- Oblique fracture** -- bone breaks at an angle. **- Pathologic fracture** -- caused by an underlying disease (e.g. osteoporosis). **- Stress fracture** -- hairline crack. [Repair/Healing of fracture:] 3 phases of repair involved: **- Reactive phase** -- early inflammatory phase with blood clot (fracture hematoma) and influx of immune cells occurs. Osteoclasts remove dead cells. Lasts from a couple hours after fracture to several weeks. **- Reparative phase** -- Step1: Formation of fibrous cartilage callus to bridge the gap. Proliferation & growth of blood vessels, fibroblasts invade the periosteum and make cartilage. Takes \~3 weeks... Step 2: Formation of bony callus by osteoprogenitor cells that differentiates into osteoblasts. Spongy bone trabeculae are formed and they join to form bony callus. Takes additional weeks. **- Bone remodeling phase** -- final phase involves dead bone resorption by osteoclasts, compact bone formation. Several additional months to a year post fracture.