Locomotor Review Notes.docx

Locomotor Review Notes 1. Introduction to Locomotor Learning Objectives Introduce the basic arrangement of the musculoskeletal system Introduce the types and ranges of movement possible in the musculoskeletal system and how these are brought about by the muscles 2. The Shoulder Learning Objectives I...

Locomotor Review Notes 1. Introduction to Locomotor Learning Objectives Introduce the basic arrangement of the musculoskeletal system Introduce the types and ranges of movement possible in the musculoskeletal system and how these are brought about by the muscles 2. The Shoulder Learning Objectives Identify the bones, their arrangement and joints that comprise the pectoral girdle Understand the functional anatomy of the glenohumeral joint and its modifications for allowing movement. Understand the clinical relevance of these modifications Understand the movements of the shoulder and the muscles that produce these movements 1. The Shoulder Region Overview Pectoral, scapular, lateral supraclavicular The pectoral girdle is a bony ring that is incomplete posteriorly. It is formed by the scapula and clavicles. Anteriorly it is completed by the manubrium of the sternum. Elevation and depression as well as retraction and protraction of the shoulder are possible. Bones of the pectoral girdle: Clavicle: S shaped bone keeps arm away from the thorax, giving a wide range of movement as well as resilience. Can absorb shock as it acts similarly to a spring (also means it breaks often) Sternoclavicular joint: only attachment of upper limb to trunk Acromioclavicular joint: articulation with acromion of scapula Fractures of clavicle: result of direct/indirect force Anterior fragment: drawn inferiorly by weight of arms Medial: sternocleidomastoid pulls it superiorly. Most fractured bone in childhood, makes up 2-5% of adult fractures. Dangerous as it protects the branchial plexus, major vessels, apex (lung) Scapula: triangular flat bone (postolateral aspect of thorax): overlies the second and seventh ribs. Attachment site for many shoulder muscles. Physiological Scapulothoracic Joint: formed by the convex surface of the posterior thoracic cage and the concave surface of the anterior scapula (not a synovial joint). Spine (posteriorly): separates supraspinous and infraspinous fossa. Acromion: lateral end of spine, stops humerus from going too far upwards. Humerus: largest bone in upper limb. Articulates with scapula at glenohumeral joint. Contains “ridges”: greater and lesser tuberosity: attachment points for muscles from scapula. 2. Joints of the Shoulder Region Sternoclavicular: clavicle and manubrium of the sternum and 1st costal cartilage. Very strong joint, clavicle will break before it dislocates. Strength from ligaments (e.g. costoclavicular ligament between the clavicle and first rib). Only articulation between upper limb and axial skeleton. Acromioclavicular: Not as strong as SC joint. Located 2-3cm from point of shoulder. No muscles cross it, and muscles moving scapula move AC joint. Movement of the scapular: Elevation: trapezius (descending) Depression: gravity Protraction: serratus anterior, pectoralis major Retraction: trapezius (middle) Upward Rotation: trapezius (descending), serratus anterior (inferior Downward Rotation: latissimus dorsi Glenohumeral joint: glenoid cavity and head of humerus. Shallow glenoid cavity deepened by ring of fibrocartilage “glenoid labrum”. Fibrous joint capsule loose and baggy. Large freedom of movement ‘laxity’ (loose ligament) of articular capsule. Large humeral head compared to shallow/small glenoid cavity. Movements: Flexion-extension Abduction-Adduction Medial and Lateral Rotation Circumduction Muscles acting on GH joint: Chief flexors: pectoralis major (clavicular part) and deltoid (anterior part). Coracobrachialis assisted by biceps brachii: stabilize the joint. Chief extensors: latissimus dorsi, and deltoid (posterior fibers), teres major, long head of triceps brachii (stabilize) Chief abductors: deltoid (all parts but especially central fibers) 110 to 180 of abduction. Supraspinatus does the 1st 10 degrees (works with deltoid 10-110). Chief adductors: pectoralis major and latissimus dorsi (gravity is prime mover). Chief medial rotator: subscapularis (lesser tubercle) Chief lateral rotator: infraspinatus (greater tubercle) These are the rotator cuff muscles (also the teres minor GT and subscapularis lesser tubercle. Stabilize the glenohumeral joint. Form a musculotendinous ‘cuff’ around the GH joint blending with articular capsule. Have tonic contraction hold head of humerus in glenoid fossa Physiological Scapulothoracic Joint: head of humerus (four times bigger then glenoid fossa) uses all available articular surface at 90. Scapula rotates to allow remainder (serratus anterior and trapezius) For 15 of shoulder abduction: glenohumeral joint gives 10, scapulothoracic joint gives 5. 3. Bursae A fluid filled sac: acts as a cushion to reduce friction. Sub acromial bursa inflammation (bursitis) causes pain on abduction. 4. Dislocation of glenohumeral joint Anterior dislocation: tilts head of humerus inferiorly onto weaker part of joint (due to gravity). Flexor and abductor muscles pull it anteriorly. Can also cause damage to axillary nerve: innervates deltoid impaired abduction, loss of sensation of regimental badge. 3. The Elbow Learning Objectives Can identify the bones and the osteology of the elbow joint Name the joints of the elbow, the movements of the elbow, and the muscles that produce these movements. Know the passage of blood vessels and nerves through the elbow region 1. Elbow Joint Consists of three joints that share the same articular capsule: Humero-ulnar: trochlea of humerus with coronoid process of ulna. Humero-radial: spheroidal capitulum of humerus with head radius These two joints allow for flexion. Proximal radio-ulnar joint: third joint of the elbow, proximal because there is another one at the wrist. Allows for rotational movement of supination and pronation. Distal Humerus: has various features Epicondyles (medial and lateral): round protuberance at the end of bones. Allows for muscle attachment (e.g. flexors in forearm start at the medial, extensors at the lateral). Condyles (two articular surfaces) Lateral: capitulum Medial: trochlea Two fossa anteriorly (radial and coronoid fossa) and one posteriorly (olecranon fossa). 2. Bones of the forearm Ulna: medial bone stabilizing bone of the arm, large proximal end specialized for articulation. Does not articulate with wrist bones distally. Radius: lateral bone: mobile bone of the forearm that rotates around the ulnar. Does articulate with wrist bones: to turn hand we need to move radius. Large distal end. 3. Ligaments of the Elbow Joint Ligaments attach bone to bone. Collateral ligaments: on the sides of the joint, take the names of the bones (e.g. ulna collateral ligament attaches medial epicondyle to head of ulnar). Anular ligament: goes around the head of the radius. Stops radius from moving away from the humerus and ulna. Allows for pivot. Biceps brachii tendon: inserts onto the radius at the bicipital tuberosity. 4. Bursae around the elbow joint (Bursae: fluid filled cushions which help to protect and provide cushioning for the tendons that could get damaged/rub onto bone). Types: Deep (subtendinous) olecranon bursa: between olecranon, triceps tendon Superficial (subcutaneous) olecranon bursa: located in subcutaneous connective tissue posteriorly to the olecranon. Intratendinous olecranon bursa: variable, present in only some people. Bursitis: generally, affects superficial bursa (known as ‘students elbow). 5. Carrying angle of the elbow Position of humerus and bones of forearm: different for men and women. Men: 5-15 degrees (average ~ 6.7) Women: 10-25 degrees (average ~13.6) Allows forearm to clear of hips (carrying objects). 6. Muscles that move the elbow joint Chief Elbow Flexor: Biceps brachii (when already flexed to 90 and supine). Brachialis: lies inferior to the biceps. Brachioradialis: stronger when forearm is in imposition. Mainly a stabilizing muscle (compared to a flexor) as it attaches to the distal radius and does not generate much force. Chief Elbow Extensor: Triceps brachii (long, lateral and medial heads). Anconeus (not really, helps triceps). Chief Supinator Muscles: Swan position Biceps brachii (with forearm in pronation). Supinator. Chief Pronator Muscles: Pronator teres (elbow) Pronator quadratus (wrist) Pronator muscles are weak compared to supinator muscles. Dislocation of elbow children: proximal radio-ulnar joint (also known as nursemaid’s elbow) Adult elbow dislocation: dislocation humero-ulna joint. Due to hyperextension, mainly happens posteriorly. 7. Cubital Fossa Shallow triangular depression on anterior surface of elbow. Boundaries: Superior: imaginary line between medial and lateral epicondyles Medially: pronator teres Laterally: Brachioradialis Floor: brachialis and supinator Roof: Brachial, antebrachial deep fascia. 8. Compartments Muscles of similar purpose and innervation are grouped within same fascial compartments (fascia) Consists of the anterior (flexor-pronator compartment) and posterior (extensor-supinator compartment) compartments, separated by the interosseous membrane. Supracondylar fractures: movement forward of humerus can damaged medial nerve, brachial artery Medial epicondyle fracture: usually breaks off due to fall on elbow. Can potentially trap the ulnar nerve which runs posteriorly. Fractured elbow (fractured olecranon): olecranon pulled away by triceps. Pinning is usually required, healing slow. 5. Neurovascular Supply of the Upper Limb Learning Objectives Describe the course of the major arteries of the upper limb Identify positions where arterial pulses may be felt Describe the formation of the brachial plexus Explain briefly the most common nerve injuries to the upper limb 1. Blood Supply Starts/ends with the subclavian arteries/veins. There is collateral circulation around the joints, and venous return is deep and superficial (superficial deep on its return to the heart). Axillary and brachial arteries: the subclavian runs over the first rib with the clavicle superiorly. Axillary: continuation of the subclavian: starting point is the inferior/lateral border of the first rib. Rubs underneath the pectoral major. Gives up pectoral artery, lateral thoracic artery and circumflex humeral artery (humerus head). Branchial starts at lower border of the teres major. Brachial pulse: medial to distal tendon of biceps brachii. Radial and ulnar arteries: Brachial artery splits at the cubital fossa. Ulnar: bigger of the branches. Both are situated in the anterior compartment. The posterior interosseous artery comes from the ulnar, goes through the interosseous membrane and supplies the posterior compartment. Radial Pulse: lateral to tendon of FCR. Ulnar Pulse: lateral to tendon of FCU (runs deeper, under fascia) Deep and palmar arches: contributions from both the radial (supplies mainly superficial) and ulnar (supplies mainly the deep). Digital arteries from both. 2. Compartment Syndrome Increased material in a compartment (due to damage to an artery, buildup of fluid) increases pressure. Pressure closes capillary beds and can eventually lead to the collapse of arteries can lead to ischemia. Symptoms: Paresthesia’s (pins and needles) Pulseless, feel cold (no circulation) Treatment: fasciotomy: cut the fascia to release pressure. Often in anterior compartment. 3. Venous Drainage Deep veins: take the name of the artery: often two veins for one artery. Superficial: outside deep fascia: basilic medial side, cephalic lateral side (ABC, A = body). These two veins interlink across the anterior of the cubital fossa medial antecubital vein. 4. Brachial Plexus Five nerve routes: C5, C6, C7, C8, T1. Located in the superior border of clavicle lateral to the sternocleidomastoid. All motor and sensory information to upper limbs. Mu: C5-7 A: C5-C6 Me: C6-T1 R: C5-T1 U: C8-T1 Dermatome: plexus: spinal nerve roots contribute to multiple nerves. C4: shoulder region C5: lateral part of arm C6: lateral part of forearm and thumb C7: middle finger C8: medial part of hand T1: medial part of upper limb 5. Branchial Plexus Injuries (Superior injury) Erb-Duchenne Palsy: most common injury. Caused by stretching of brachial plexus in birth, backpackers (constant weight on shoulders), hitting shoulder after fall (cycle, horse). Results in: loss of sensation lateral aspect of arm (C5-C6) as well as paralysis of muscles of shoulder and arm (biceps, brachialis, deltoid, infraspinatus). Appearance/symptoms Adducted shoulder, medially rotated arm, extended elbow (only triceps working), pronated elbow (biceps is main supinator), wrist flexed if C7 is involved (waiters tip) (Inferior injury) Klumpke Palsy: (C8-T1) caused by pulling of arm during childbirth, abrupt stop during fall. Paralysis is mainly to the ulnar nerve. Can cause claw hand paralysis of small muscles in hand. 6. Important nerves from brachial plexus: do not enter upper limb Long thoracic: C5, C6, C7. Innervates serratus anterior (holds scapula onto posterior part of ribcage so scapula does not move away when pushed). Also, important for scapula thoracic joint: allows for abduction. Loss in muscle unable to lift arms fully. Thoracodorsal (C6, C7, C8): not important at this point. Suprascapular: supraspinatus, infraspinatus. Comes from C4, C5, C6. 7. Branches of branchial plexus Posterior chords: axillary and radial Axillary: innervates deltoid. If damaged: loss of sensation over lateral arm. Caused by dislocated shoulder, fractures of humerus surgical neck. Radial is the largest, innervates all extensors of the upper limb. Paralysis means you will lose sensation in a bit of skin innervated just by the radial nerve: 1st dorsal interosseous web (skin between thumb and index finger). Anterior chords: median, ulnar and musculocutaneous. Ulnar: innervates flexors in the forearm (FCU, medial half of FDG) and intrinsic muscles (hand). Can be identified by loss of sensation in little finger, most often caused by fracture of medial epicondyle. Musculocutaneous nerve: injury uncommon: well protected. If injured, paralysis of BBC (biceps, brachialis, coracobrachialis as it innervates these muscles Median nerve: innervates all pronators and flexors of forearm not innervated by ulnar as well as the thenar muscles. Paralysis: most digit flexors and muscles moving thumb, index finger Long term causes atrophy of thenar muscles. Due to supracondylar fractures, compression of wrist. 6. Movements of the hand: forearm and anatomy Learning Objectives Describe the actions of the muscles (both intrinsic and extrinsic) that are used to open and close the hand Define the term opposition of the hand Understand the movements that are possible at the various joints of the hand 1. Bones in the hand Metacarpals: articulate with proximal phalanges via the metacarpophalangeal joint (MCP). Allows for movements of flexion, extension, abduction, adduction. Phalanges: contain proximal interphalangeal and distal interphalangeal joints for flexion, extension. (Phalanges consist of a proximal, middle, distal part). Thumb only has two. The thumb (digit 1): has 1 MCP, 1 interphalangeal. Flexion moves thumb across palm of hand (closer to little finger). Extension is opposite. Abduction: takes thumb away from palm at right angles, adduction is the opposite. Opposition: combination of flexion, medial rotation and abduction. Muscles that move the fingers: Intrinsic: partly in the hand Extrinsic: partly in the forearm. 2. Compartments of the forearm Includes the distal humerus: Flexors: share a common original in the medial epicondyle Extensors: share a common origin in the lateral epicondyle. Superficial flexors (anterior): consist of four muscles superficially: Pronator teres Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Middle: flexor digitorum superficialis Deep (inferior): Flexor pollicis longus Flexor digitorum profundus Tendons of the FDS and FDP enter common flexor sheath deep to the flexor retinaculum. In the central compartment, they separate into respective digital synovial sheath. This synovial sheath is held in place by fibrous digital tendon sheath. Ganglion cysts: tendons sheaths can split and tear and synovial fluid can leak out. However, proteoglycan it contains remains behind and forms a cyst at the tear (very common). 3. Carpal Tunnel Passageway on the palmar side (anterior) of the wrist that connects the forearm to the hand Lies underneath the flexor retinaculum (fibrous band on palmar side of hand near wrist. Arches over carpal bones of hands, covering them and forming the carpal tunnel). 4. Flexors in the digits The tendon flexor digitorum superficialis (flexes MCP and PIP), splits into two (inferiorly) to allow passage of the flexor digitorum profundus (flexes MCP, PIP, DIP) to a more distal insertion point. Flexor pollicis longus: flexes MCP and IP of thumb. (NOTE: extensors insert on dorsal surface of fingers: green). More complex fibrous tissue. Trigger finger: if tendons of FDS and FDP enlarge proximal to tendon sheath person is enable to extend finger. Extended passively: snap is audible as tendon moves back into sheath. 5. Muscles opening hand (extensors) Located on the posterior side of the forearm. Consists of: Extensor digitorum communis: 4 tendons. Extensor indicis: index finger Extensor digiti minimi: little finger. Abductor pollicis longus, extensor pollicis brevis, extensor pollicis longs: for thumb. Tendons run over wrist: more complicated. There are tendon sheaths for little group of muscles. Only important one: sheath 1: contains APL, EPB. Is on the most lateral part, base of the thumb. 6. Intrinsic Muscles of the hand Thenar muscles: (consists of three muscles) act on the thumb Hypothenar muscles: (consists of three muscles) act on the little finger. Lumbricals: flex the MCP, extend interphalangeal joints of 2nd-5th digits. Dorsal interossei: abduct the 2nd to 4th digits. Assist Lumbricals Palmar interossei: adduct the 2nd, 4th and 5th digits. Assist Lumbricals 7. Compartments of the hand Fascia of palm and dorsum of hand continuous with antebrachial fascia (deep fascia surrounding forearm). Thin over thenar and hypothenar muscles thick in central area. Two potential spaces: midpalmar and thenar bounded by fibrous muscle septa. Dupuyten’s contracture: fixed flexion contracture on the hand. Palmar fascia thickens as collagen I is replaced by collagen type III. Happens in many northern Europeans, men (10:1), >40 years. 7. Overview of Upper Limb Learning Objectives to understand the functional anatomy of the upper limb to understand the modifications for movement and the clinical relevance of these modifications understand the 2 main categories of grip and the main sub-divisions within each understand how nerve damage can affect the function of the hand 1. Types of grip: Power Grips: all fingers flexed around object (found in babies). All muscles closing hand are active. Hypothenar muscles stabilize medial side of palm. Wrist extensors active: provide stable base. Precision grip: object held between tip of thumb and 1, 2, 3 fingers. Intrinsic muscles involved, co-operate with long flexors and extensor muscles. More advanced: ~ 9 months after birth. 2. Radial Nerve Posterior chord: travels from glenohumeral joint to posterior compartment to innervate extensors. Runs in the radial groove at the back of the humerus. Injury: fractures midshaft. Clinical symptoms: wrist drop (no extension of wrist and digits). Weak flexion at DIP joint from intrinsic muscles of the hand. Loss of sensation back of forearm. Saturday night palsy: radial nerve in armpit or upper arm is compressed/stretched. Usually falling asleep with arm hanging. Palsy in newborns: due to prolonger pressure on inferior arm by pelvic brim. 3. Median Nerve Anterior. Travels on medial side, very superficial in the cuboidal fossa and into anterior compartment of forearm innervates flexors of wrist and forearm (except for FCU and medial half of FDP: these are innervated by ulnar nerve. Goes through the carpel tunnel and innervates thenar group. Injury: two types: High median nerve injury: supracondylar fractures of humerus (at elbow). Patient is unable to make a fist: loss of flexion of MCP, DIP in digits 2-3, loss of flexion of PIP in digits 1-3. Weak PIP flexion in digits 4-5. Can flex DIP digits 4-5 because of ulnar innervation. (Low) Carpal tunnel syndrome: any condition reducing size of carpal tunnel causes compression of median nerve. Fist can be made, but not as strong. Thenar muscles don’t work (can lead to atrophy: loss of mass) 4. Ulnar Nerve Innervates flexors in the forearm (FCU, medial half of FDG) and intrinsic muscles (hand). Most commonly injured (~27%). Happens often at the medial epicondyle of humerus. Leads to claw hand (thumb abducted and extended with distal phalanx flexed, first 2 fingers extended, medial 2 fingers hyperextended at MCP joint but flexed at DIP joints). Indicative of muscles involved: Flexor carpi ulnaris Medial half of FDP Medial two Lumbricals All interossei (palmar and dorsal) 8. Radiological Imaging of the Skeletal System Learning Objectives Describe the main features of other imaging modalitites for imaging the skeletal system. Understand additional X-Ray based imaging techniques for specialized imaging of the skeletal system Understand the advantages and disadvantages of X-Rays for imaging the skeletal system 1. General Considerations Images are used for assessment of trauma, degenerative diseases, metabolic diseases, infections, neoplasms (a new and abnormal growth of tissue in a part of the body). 2. Terminology Lucent Lesions of bone: area of bone looks darker (bone is lost/damaged) Sclerotic Lesions of bone: white area, certain process has bone look denser. Periosteal reaction: fracture/damage: bone cells go back into cell cycle, push periosteum away, leads to the loss of smooth edges. Soft Tissue Calcifications: white patches in the soft tissue Osteopenia: localized reduction in bone density Osteonecrosis: death of bone with loss of shape Fractures: discontinuity of bone, black lines separating pieces. Orthopedic hardware: anything that is denser than bone shows up Joint integrity: loss of joint space/joint orientation. BEWARE: Rotation/movement can change the way bones look. Also, different views of the same structure can help (e.g. supero inferior view next to AP view). X-rays of children are different: cartilage does not show up so looks like some bones are floating in empty space when they are not in reality. Example: formation of the femur. (Right image): head of femur looks like semi-circle. Again, this is in child: there is an epiphyseal growth plate in between which is not seen. (Left image): also of a young child, but has certain condition: congenital dysplasia of the hip: head of femur is not associated with acetabulum). 3. Abnormal in X-Rays Things to look out for: Shape, size, orientation of bones and joint surfaces Breaks in the bone Extra bone Loss of bone Foreign objects 4. Limitations Only calcified tissue shows up clearly Not very sensitive – you must lose 30% of bone mass before it appears on x-ray Things in front can obstruct structures behind – e.g. hard to see patella, processes within the bone cannot be seen. 5. Other Scans Arthrogram: Iodine contrast media injected into the joint cavity along with air DEXA scan = duel energy x-ray absorptiometry Uses 2 different low energy x ray sources Improves accuracy Can also be used for body composition (fat) 9. Bone Ossification, Growth, and Basic Bone Metabolism Learning Objectives To describe the process of intramembranous and endochondral bone formation To describe how bones, grow postnatally To describe normal adult bone metabolism 1. Normal Bone Structure Consists of lamellar bone (layers): Cortical: ~ 80% of adult skeleton. Dense section on the outside of bone that gives the bone it’s outer rigidity and strength. Cancellous/trabecular bone: ~20% of adult skeleton. Found in heads and centers of bone. Another type of bone that exists is woven bone, used in healing and occurs in babies/children. Bone is made up of columns (osteons: circular structures) stacked on top of each other. They run the length of the diaphysis (the shaft of the bone). Bone Composition: The matrix of the bone is 35-40% organic: 28% collagen (mainly type 1 for tensile strength) 5%: proteoglycans/glycoproteins (compressive strength and calcium binding), osteocalcin (bone promoting growth factor) 60% of bone is inorganic. This part is made up of 95% calcium hydroxyapatite (precipitated collagen network). Remainder is 5% water. Bone Cells: Osteoprogenitor cell: differentiate into osteoblasts from mesenchymal cells. Osteoblasts: active bone builders: secrete collagen, proteoglycans\, osteoid. Osteocytes: maintaining the bone make collagen, proteoglycan, osteoid at lesser rate Osteoclast: move in to destroy the bone (multinucleate macrophage cells). 2. Ossification Begins 6th or 7th week of intrauterine life. Two methods that give the same outcome Intramembranous Mainly in the skull Mesenchymal cells from mesenchymal tissue differentiate into osteoblasts. Osteoblasts: forms centers of ossification by secretion of bone matrix/osteoid. Osteoid (matrix) is mineralized to form bone spicules. Centers grow around fetal blood vessels until they meet for form trabeculae. Mesenchyme on the external face of the woven bone condenses and becomes the periosteum. This is then remodeled to form lamellar compact bone. Endochondral Ossification In this type (formation of longer bones): mesenchymal tissue condenses and differentiates into chondroblasts which forms hyaline cartilage model. Perichondrium forms this model. Chondroblasts become encased in the cartilage matrix. Chondrocytes in center undergo hypertrophy: they stop secreting collagen and begin secreting alkaline phosphatases. This generates an alkaline environment needed for the calcification process. Some cells hypertrophied chondrocytes burst leaving small cavities. Bone collar: mid-section thin layer of bone forms around outside of model periosteum. Nutrient artery enters developing bone via nutrient foramen. Capillaries grow into cartilage model: carry osteogenic cells. These secrete osteoid, form primary ossification center Bone is remodeled as it grows, and primary ossification centers grow towards ends of the bone. At the top: blood vessels grow into epiphysis, bring osteogenic cells and bone marrow, forms a secondary ossification center. Cartilage in between the two centers. Hyaline cartilage remains over the end of epiphyses (forms articular cartilage) Hyaline cartilage remains between diaphysis and epiphysis. This forms the epiphyseal growth plate. Remaining cartilage allows bone to growth through puberty. Epiphyseal Growth Plate Epiphyseal growth plate: active/open until 18-25 years then closes. Clavicle last bone to fully ossify. 3. Bone Growth Appositional growth: bone grows in thickness. More bone, laid down by osteoblasts in the periosteum, more cartilage by chondroblasts and expansion of matrix. 4. Bone Remodeling Occurs to renew bone before deterioration as well as redistributes bone matrix along mechanical lines of stress. Trabecular bone is remodeled three to ten times quicker than cortical bone (responds to stresses on bone quicker). Remodeling is signaled by the following: Osteocytes: Cellular processes extend in canaliculi and touch their neighbors. Signal by switching off growth factor (sclerostin): stops bone formation. Signals osteoblasts to start producing more bone. Osteoclasts: bone resorption by osteoclasts. Mechanism by which they work: Attach to bone forming leak proof seal Release protein-digesting enzymes and acid (HCI) underneath. Enzymes break down collagen, HCL dissolves calcium hydroxyapatite. Bone proteins, minerals (mainly Ca2+) cross osteoclast, exit into IF. Then, osteoblasts fill lacuna with osteoid: osteoid is mineralized (approx. 7-10 days for new osteoid to be mineralized). 5. Bone metabolism Serum calcium: maintained between 2.2-2.6mmol/L. Low plasma Ca2+ stimulates parathyroid hormone (PTH) secretion from the parathyroid glands. Promotes the following: Ca2+ reabsorption from kidney and PO4 excretion Ca2+ reabsorption from bone: increases number/activity of osteoclasts. Synthesis of 1,25-dihydroxyvitamin D (1,25 (OH)2 vitamin D3) 1,25 (OH)2 vitamin D3 increases Ca2+ absorption from gut If too high: calcitonin release from the C-cells in thyroid gland. Inhibits osteoclast resorption. Low 1,25 (OH)2 vitamin D3 - abnormal mineralization of new osteoid due to low Ca2+ and PO4 availability and reduced osteoblast function Other hormones: Oestrogen Gut - increased Ca2+ absorption Bone - decreased re-absorption (inhibits osteoclasts) At menopause loss of bone mass – osteoporosis Gut - decrease Ca2+ absorption Bone - increased re-absorption / decreased formation Prolonged corticosteroid treatment – osteoporosis 10. Joint Structure and Function Learning Objectives to identify the three main types of joint and how structurally they influence the amount of movement possible understand the components of a synovial joint describe the different types of synovial joints understand how the articular cartilage contributes to the function of synovial joints A joint (articulation/arthrosis): point of contact between two or more bones. Classified as fibrous, cartilaginous or synovial. 1. Fibrous Joints: Are solid, articulating bones held by connective tissue. No cavity, little or no movement. Types: Sutures: skull premature sutures are fontanelles (anterior being the largest). Synostosis: two bones fused together (ossified) Syndesmosis: sheet of fibrous tissue between bones (only two: tibia/fibula, ulnar/radius). Separates the anterior from the posterior compartment. Gomphosis: cone-shaped peg fits into socket (e.g. teeth). 2. Cartilaginous Joints Again, no synovial cavity so little or no movement. Articulating bone connected by fibrocartilage or hyaline cartilage (epiphyseal growth plates). Types: Synchrondosis: connected by hyaline cartilage. Temporary: disappear in grown adult. Symphysis: connected by fibrocartilage (permanent). Two different types: Pubic symphysis: allow for compression. Intervertebral discs: connects vertebrae above and below. NOTE: fibrocartilage gives more bend than hyaline cartilage. 3. Synovial Joints (diarthroses) Synovial (joint) cavity between articulating bones. Mainly in appendicular skeleton. Freely movable. Following components: Articular (fibrous capsule) Synovial membrane Synovial cavity (contains synovial fluid). Articular cartilage. NOTE: Bursae are often just extensions form the joint cavity (they are also filled with synovial fluid). Structure: Articular cartilage hyaline cartilage. Smooth, slippery and very low coefficient of friction. Acts as a shock absorber due to its elastic and resilient structure. Deep layer of cartilage merges with calcified layer of subchondral bone. Properties depend on composition of ECM (usually ~80% water, contain collagen type II instead of collagen type I in bone, as well as proteoglycans) Proteoglycan: negative charge, helps to keep water in articular cartilage. These joints contain also contain: Accessory Ligaments: connect bone to bone (dense regular c.t.) Articular discs (menisci): modify shape of joint surfaces. Help maintain stability of joint, direct flow of synovial fluid to areas of greatest friction. Articular capsule Encloses synovial cavity, unites the two bones. Layers: Outer fibrous capsule (may contain ligaments) Inner synovial membrane (secretes lubricating and joint nourishing synovial fluid): structure looked at in 11. NOTE: loss of joint space (osteoarthritis) is not the space that is being lost but cartilage (articular cartilage being degenerated). Exposes underlying bone. 4. Types of Synovial Joints: Plantar joints: allows side to side, back and forth gliding movements (examples intercarpals or intertarsals). Hinge joints: convex surface of one bone fits into concave of another. Allows for flexion and extension on a single plane. E.g. Elbow. Pivot Joint: round or pointed surface of one bone fits into ring of another (and ligament). Allows for rotational movement. Example: atlas and axis (C1, C2). Ellipsoidal Joint: oval shaped condyle of one bone fits into elliptical cavity of another. Allows movements of flexion, extension, abduction, adduction and circumduction (example: between carpals and radius, wrist joint). Saddle Joint: one bone is saddle-shaped, the other is the rider. Movements of flexion-extension, abduction-adduction, circumduction (e.g. carpometacarpal: rider is the trapezium metacarpal of the thumb is the saddle. Ball and socket joint: ball-shaped surface of one bone fits into cup-like depression of other. Movements of flexion-extension, abduction-adduction, rotation, circumduction (example, shoulder and hip joints). 11. Synovial Fluid and Articular Cartilage Learning Objectives understand how the articular cartilage contributes to the function of synovial joints. understand the main biochemical components of synovial fluid. understand how glycosaminoglycans contribute to lubricating properties of the synovial fluid understand how synovial fluid is produced. 1. Synovial Membrane Is one to three cells thick. Epithelium is made up of Synoviocytes Synoviocytes: make proteoglycan to make fluid stick together. Type A Bone Marrow Derived Macrophage: immune purpose Type B Fibroblast-like connective tissue cell: makes proteoglycans that are added to synovial fluid. There is no basement membrane between the synoviocytes and subintima. Subintima: contains dense network fenestrated capillaries. This means it is very leaky, and allows synovial fluid to come out of blood vessels and enter joint cavity (fibroblasts cells add hyaluronic acid, sf is an ultra-filtrate of blood). Forms a thin film over surfaces in articular capsule (1-2mls only). Appearance: should be transparent, yellowish color. Component Value pH 7.38 WBCs (/mm^3) 63 (phagocytes) Hyaluronate (g/dl): main proteoglycan 0.3 (3-4mg/ml) Glucose (mmol/L): dissolved from blood 4.0 Protein (g/dl) (Albumin: 60%, Globulin: 40%). 1.8 Lubricin 2. Composition of synovial fluid Also, contains ions, lactate etc… Rheumatoid Arthritis: Affects synovial fluid (autoimmune conditions where synovial membrane becomes inflamed). Osteoarthritis mainly impacts articular cartilage. 3. Synovial Fluid Small amount occupies all free spaces between articulating surfaces (approx. 50um). Menisci are very important in directing the fluid. (NOTE: knee joint is the largest in the body contains 1-2mls). At rest, synovial fluid (or it’s water component) seeps into articular cartilage. Makes it slippery, as a well as nourishing the articular cartilage with glucose, oxygen and nutrients (articular cartilage is avascular and aneural (no blood and no nervous supply). Also, forms a reserve volume, and allows force to be distributed across joint surfaces. Thixotropic: Viscosity is not constant synovial fluid gels at rest and has a higher viscosity compared to in movement, where it is less viscous (water forced from articular cartilages when compressed weeping lubrication. Hyalurononan/hyaluronic acid: Hyaluronate is a glycosaminoglycan (GAG). It forms a moisture “grabbing” network which can hold water to make it thick and compressible. High/fast frequency movement: entangled molecular networks resists deformation and acts as a shock absorbed. Energy is stored as elasticity. Low/slow frequency movement: molecules align in direction of movement; energy is dissipated as viscous flow which allows free movement. Lubricin: water soluble glycoprotein. Equal proportions of protein and oligosaccharides. Produced by chondrocytes and synoviocytes. Sits on the surface of articular cartilage (thin barrier): due to its negative charge, it repels the two sides from each other. 4. Synovial Fluid Analysis 5. Articular Cartilage Caps the ends of bones in synovial joints. Made up of hyaline cartilage (type II collagen). Contains GAGs which form proteoglycans: gives a hydrated-like gel which allows for diffusion of nutrients, metabolites, hormones between blood and cartilage cells. Role: elastic, resilient: acts as shock absorber/compression. Similar structure to epiphyseal cartilage. Contains: Superficial zone: (parallel collagen: smooth surface) Middle zone: start to get bigger, push collagen fibers into a disorganized meshwork. Contains sockets in which proteoglycans can be put Deep zone: clear stacks, form perpendicular to surface. Gives less compression GAGs and Proteoglycans: Aggrecan is the major proteoglycan in cartilage made up of a hyaluronic acid core: has legs which also have a core protein, contain spiky hair like proteins (GAGs). Forms large proteins with negative charge. ECM: Made by chondrocytes: contains up to 80% water. Has collagen type II. Consists of a network of fibrils. Contains pockets: filled with water binding proteoglycans complexes: regulate compressibility. Lack blood and lymphatic vessels. Osteoarthritis: damage to proteoglycans 12. The Hip Learning Objectives Describe the hip joint and the functional anatomy that provides it with stability Know the movements possible at the hip joint and the muscles that produce these movements Understand the arrangement of the pelvic girdle in relation to the hip joint Understand the clinical relevance of the hip joint Shenton’s Line: imaginary line drawn along the inferior border of the superior pubic ramus (superior border of obturator foramen) and along inferomedial border of the neck of the femur. Used diagnostically for dislocations of the hip 1. The Hip Intro Ball and socket synovial join. The round head of the femur articulates with a cup-shaped acetabulum of the pelvis. Allows for a great range of movement as well as contributing to stability (weight-bearing bone). Stability: 2/3 of the head of the femur is inside the acetabulum. It contains a tight articular capsule (not loose like in shoulder) Ligaments around the joint (especially anteriorly) Fibers oriented so they are twisted when standing up: draws structures together. Large powerful muscles (such as gluteus maximus) exists around joint. Medial and lateral rotators Ligamentum teres: within arterial capsule: contains blood vessel in children. Fat pad in the middle of the femur: acts like a sponge, allows stability. 2. Acetabulum Formed by the fusion of three pelvic bones: ischium, ilium, pubis. Contains a rim of fibrocartilage: acetabular labrum. A horseshoe shape that increases the acetabular articular surface by 10%, acts as a suction cup to hold head of the femur. 3. Articular Capsule and Ligaments Contains strong thick articular capsule. Strongest and thickets ligaments (e.g. anterior iliofemoral ligament) are over upper and anterior parts. (Posterior is weaker). Anterior Iliofemoral Ligaments: prevents excessive extension of hip. Relaxed in flexion. When standing: it holds femoral head in acetabulum. Dislocation: shortening and medial rotation of leg. Posteriorly joint is less strong, so dislocation often occurs this way (foot pointing inwards). Acetabulum can also fracture with chips breaking of. Dangerous: can compress/stretch sciatic nerve behind the head of the femur. 4. Movement of the Hip Hip flexion: done by: 1. iliopsoas (made up of psoas major attaching from lumbar vertebrae and iliopsoas: anterior rim of the iliac bone). Sartorius: abducts and laterally rotates hip Pectineus: also, adducts and medially rotates 2. Rectus femoris (quadriceps). Attaches from anterior inferior iliac spine: as it goes down to the quadriceps it moves of the joint, acting upon it. Innervated by the femoral nerve Hip Extension: done by: 1. Gluteus maximus (innervation from inferior gluteal nerve). 2. Hamstrings (innervated by the tibia division of the sciatic): Hip Abduction: done by: 1. Gluteus medius and minimus (innervation by superior gluteal nerve) 2. Tensor fasciae lata: tenses iliotibial tract, takes leg out to the side (superior gluteal nerve). Hip Adduction: done by: Adductor group of muscles medial thigh: Adductor longus, brevis, magnus Gracilis Obturator externus Innervated by the obturator nerve. Hip Lateral Rotation: done by: gluteus maximus, adductors Hip medial rotation: gluteus medius/minimus, TFL 5. Iliotibial Tract Acts as a long aponeurosis (insertion points) tensor fascia latae and superficial and anterior parts of the gluteus maximus. 6. Fracture of the neck of the femur Hip fractures usually at 1 of three sites: High in femoral neck (subcapital) Across the neck (cervical) Trochanteric region (pretrochanteric) Foot is pointing laterally (not medial like dislocation). Treatment depends on age: older people (with osteoporosis) often have hip replacements. (!) A fracture to the neck of the femur may disrupt blood supply to the femoral head: avascular necrosis (blood supply comes from deep femoral artery: profunda femoris. Gives of the lateral and medial circumflex arteries. Leads to bone dying. 13. The Knee Learning Objectives Describe the extra-capsular and intra-capsular ligaments of the knee joint Be able to describe the structures that pass through the popliteal region Understand the arrangement of the bones and their osteological features that make up the knee joint Understand the function of the bursa around the knee joint 1. The Knee Joint Intro: Q-Angle: important in supporting weight of the body (would not be possible if it went straight down). Femur is angled medially. Line is drawn from the ASIS (anterior superior iliac spine) to the center of the patella. Angle is then measured. Males: 14 degrees (+/-3, same as): Females: 17 degrees (so more stress on medial side). Women more at risk of knee pain and injury. Have smaller thighs, larger Q. Because pelvis is wider so hip joints further lateral. Femur must angle more. The knee joint is the largest joint in the body: has three articulations: Lateral femoral and tibial condyles with corresponding meniscus Medial femoral and tibial condyles with corresponding meniscus Patella and femur (all share the same joint cavity). Predominantly a hinge joint: (convex into concave): allows for extension and flexion. A small amount of rotation required for full extension. Mechanically, knee joint is weak. Stability depends on: 1. Strength + actions of surrounding muscles and tendons. 2. Ligaments that connect the femur and tibia. Bursae: (extension of synovial cavity): act as cushions against friction and rubbing of tendons, ligaments, bones, around knee joint. Articularis genu: small flat muscles from vastus intermedius attach to femur and suprapatellar bursa. Keeps synovial membrane from being trapped between the patella and the femur (holds the femur and supratellar bursa up). Housemaids knee prepatellar bursitis Clergyman’s knee prepatellar and infrapatellar bursitis. Bakers cyst: associated with meniscal tears, arise from joint capsule/bursae behind knee. 2. Menisci Medial and lateral menisci: crescent/horseshoe shapes of fibrocartilage. Outer edge: thick and attach to joint capsule vs inner edge: essentially unattached. Medial more commonly injured than lateral (attached to medial collateral ligament and ACL). 3. Articular Ligaments Lateral collateral ligament (fibular): from lateral epicondyle fibula Not attached to the joint capsule or lateral meniscus. Medial Collateral ligament (tibial): broad, flat ligament. Blends with joint capsule, attached to the medial meniscus. Prevents knee abduction. Anterior cruciate ligament: stops tibia moving forward on femur. Runs medial (tibia) to lateral femoral condyle. Stops tibia from moving forward on femur (stabilizes in extension, prevents hyperextension and excessive internal rotation). Can be repaired by using various ligaments from the body. Posterior cruciate ligament: stops tibia from moving backward on femur. Stronger than ACL, so injury less common (a bit shorter, more vertical). Helps stabilize knee especially in flexion. 4. Patella Seasmoid (floating) embedded in the tendon and ligament. Patella ligament: continuation of quadriceps femoris tendon (anterior thigh). 5. Muscles that move the knee Flexion: done by: 1. Hamstrings. Innervated by sciatic nerve Semimembranosus Semitendinosus Biceps femoris 2. Popliteus Weakly flexes knee Innervated by tibial nerve Unlocks knee by rotating femur 5 laterally Rotates tibia medially (if foot of ground, flexed). Extension: done by: 1. Quadriceps (4 muscles at the front of the thigh) Innervated by femoral nerve Rectus femoris Vastus lateralis Vastus medialis Vastus intermedialis 14. Neurovascular Supply Learning Objectives Be able to describe the course of the major arteries in the lower limb. Be able to describe the course of nerves in the lower limb. Describe the formation of the lumbar and sacral plexi Be able to identify where arterial pulsations may be felt in the lower limb Know the functional problems arising from damage to nerves in the lower limb and the lumbar and sacral plexi Know the mechanisms by which blood returns from the veins of the lower limb to the heart. 1. General Blood Supply to Lower Limb Abdominal aorta bifurcates at L4. Splits into internal and external iliac at L5 Internal Iliac: gives of the obturator and superior gluteal arteries. Externa iliac: becomes the femoral artery as it passes under the inguinal lig. Just under this it gives of the profunda femoris branch (gives blood supply to the quadriceps and the hamstrings, as well as lateral circumflex). Femoral pulse: below inguinal ligament and mid-inguinal point (half-way pubic symphysis, anterior superior iliac spine starting point of inguinal ligament) Femoral Artery: Moves from anterior to posterior compartment through a defect in one of the adductor tendons (adductor hiatus). Changes its name to popliteal. Popliteal artery: passes through popliteal fossa, back of knee. Anterior tibial artery Posterior tibial artery: Posterior compartment > anterior, needs a dual supply. Gives of another branch: fibular (peroneal) on the lateral side Popliteal pulse: difficult to find (deep in popliteal fossa). Knee flexed: relax the popliteal fascia and hamstrings (feel medially). Dorsalis pedis pulse lateral to extensor hallicus longus), Posterior tibial pulse: half-way between medial malleolus and calcaneal tendon 2. Veins Deep Veins: same name as arteries Superficial Veins: lies outside fascia Small saphenous: lateral part foot, ends in popliteal veins (travels laterally, under knee). Great saphenous: starts at the dorsum of the foot, travels up medially. Control of venous return: Movement superficial to deep veins Respiratory pump, muscular pumps Smooth muscle (Venoconstriction) and valves. Varicose: valves become impotent. 3. Lumbar Plexus (L1-L4) Three important nerves: Femoral: (L2, L3, L4) MOTOR: innervate the quadriceps SENSORY: skin on anterior thigh and medial leg Lateral Cutaneous: purely sensory to lateral thigh (L1, L2) Obturator (L2, L3, L4) MOTOR: all adductor group of muscles SENSORY: innervates skin over medial though 4. Sacral Plexus (L4-S4). Three main branches: Superior gluteal: (L4, L5 S1) MOTOR: gluteus medius, minimus and tensor fascia lata (abductors) Inferior gluteal: ((L5-S2) only MOTOR: gluteus maximus Sciatic: (L4, L5, S1, S2, S3). Consists of two portions: Tibial portion: MOTOR: all muscles in posterior compartment of thigh, posterior compartment of leg, all muscles in the sole of the foot SENSORY: postolateral, medial surfaces of foot, as well as sole of foot Fibular (common peroneal): MOTOR: all muscles in anterior and lateral compartments of the leg and the extensor digitorum brevis. SENSORY: anterolateral of leg, dorsal aspect of foot. 5. Summary 15. The Ankle and Foot Learning Objectives Understand the ankle joint proper (talocrual joint), and the sub-talar joints to the movements of the ankle and foot. Understand the functional anatomy of the foot. 1. The Ankle Joint Allows for dorsiflexion and plantarflexion. Stability: talus wider anteriorly (support body weight). Plantar flexion: moves posteriorly wobble. Ligaments: Medial ligament (deltoid: triangular shape): medial malleolus of tibia to calcaneus and navicular. Stops talus moving out. Lateral ligament: Three separate ligaments: Anterior talofibular Posterior talofibular Calcaneofibular Sprained ankle: stretching/tearing of anterior talofibular, calcaneofibular. 2. Muscles that move ankle Dorsiflexion and toe extension (anterior compartment): Innervated by common peroneal nerve: deep branch TA = Tibialis anterior EDL = E. digitorum longus EHL = E. halluces longus Eversion (lateral compartment) Innervated by common peroneal nerve (superficial). FB = fibularis longus FB = fibularis brevis Plantar flexion: Superficial and deep flexors Superficial: attach via calcaneal tendon Gastrocnemius Sol = Soleus Plantaris Deep muscles attach to bones of foot: Tibialis posterior (inverts) Digitorum Longus F hallicus longus Rupture of Calcaneal tendon: strongest tendon in body. Pushes the heel of the ground against body weight. If it tears: muscles shoot up the leg. Surgery required. 3. Retinacula (= connective tissue band in which tendons pass under) Extensor and flexor retinacula: hold tendons in place as they enter foot. Flexor retinacula: tibial nerve and posterior tibial artery pass under these. Extensor retinacula: deep tibular (peroneal) nerve and anterior tibial artery pass All long tendons run in synovial sheaths (like in hand). 4. The foot Talus articulates with calcaneus (posteriorly) and navicular (anteriorly). Movements: Inversion and eversion Helps the foot adjust to different surfaces. Contains numerous ligaments for stability: Medial side: spring (plantar calcaneonavicular) ligament continuous with deltoid ligament. Lateral side: long and short plantar ligaments. Contain instrinsic muscles: 4 layers. Arches: shock absorbers, energy saving Medial longitudinal = resilient (large number of bone components, missing in footprint). Lateral longitudinal = fewer bones, weight is transmitted through it by talus. Maintenance of LA arches: DYNAMIC: muscles tendons: insert into apex increase height of bones. Those that insert into the sole prevent separation. Tibialis anterior (apex) Fibularis longus (sole) PASSIVE: shapes of bones allow them to interlock. Ligaments prevent separation. Spring ligament, long and short plantar ligaments. Some people have high arch or flat foot conditions Bunions (bone deformity of big toe) Hallux Valgus Movement of great toe towards second toe. 90% inherited, can be the result of tight point shoes. 16. Walking and Posture Learning Objectives Describe the changes of moving from a double to a single support Describe the events in the normal walking cycle Understand the actions of the main muscle groups of the lower llimb in the walking cycle 1. Posture: Weight of upper body: transmitter centrally through vertebral column Ileum transfers weight to femurs (to ileum the sacroiliac joint). Pubic rami form “struts” or braces to maintain integrity of arch Diagonal (Q-angle): femur re-centers support directly under the body to make bipedal standing more efficient and help walking. Quadriceps: require simultaneous support from both sides Standing straight: center of pressure in front of ankle, just in front of knee, just behind hip, ear. Changing to a single support: when one leg lifted off the ground, muscles around the hip (such as gluteus maximus) become active (contract) Abductors: prevent pelvis from dropping to unsupporting side Adductors: help to move body weight. Trendelenburg’s sign: positive if pelvis drops to unsupporting side. 2. Walking Stance phase: begins heel strike, ends: toe leaves ground (60% of cycle). 5 phases: Initial contact: foot inverted and dorsiflexed (contact of heel on lateral side). Loading response: foot brought into full contact, Mid stance: body weight brought over planted foot. Terminal stance: heel lifted off ground (foot everted and plantar flexed). Body weight advances ahead Pre-swing (toe of): transfer of weight from one limb to other. Swing phase: begins with toe off (pre-swing initial swing). Three phases: Initial swing: foot pushes off ground, limb accelerates forward. Mid-swing: limb moves body until tibia of leg is vertical: foot is dorsiflexed, prevent dragging Terminal-swing: limb decelerates forward movement, prepares for initial contact again. 3. Muscle Groups Used Stance: dorsiflexors (tibialis anterior) active at heel strike. Gluteus maximus and hamstrings extend hip early in stance. Quadriceps extend knee (in loading response), calf muscles contract in midstance to advance bodyweight, hip abductors active when going from double to single support. Plantar flexors active at toe off to power forward thrust. Swing: hip flexors help lift leg off ground, early swing phase. Hamstrings flex the knee, lift swinging leg of the ground. Dorsiflexors active through to prevent toes dragging. 4. Abnormal gait Mechanical: osteoarthritis, muscle strains, blisters Neurological: perception deficits, nerve damage. Shuffling gait: Parkinsonian gait: short shuffling steps, rigidity in hip and knee extensors. Stooped forward posture, arm swing reduced, turning is rigid like a statue. This is because muscles stiffen as there is a loss of dopamine receptors. Scissor gait/spastic gait: thigh swings across body during swing phase (because cannot bend/flex/extend hip). Difficulty in putting heel on ground, toe often strikes first. High stepping gait: paralysis of the dorsiflexors foot drop, unless leg is lifted higher by exaggerated knee bend. Whole foot tends to slapped on ground rather than heel strike. Plantarflexor paralysis: no forward thrust. Unaffected limb never advances past affected limb. 17. Vertebrae and Vertebral Column Learning Objectives Know the arrangement of the vertebrae in the vertebral column Can identify the vertebrae from the cervical, thoracic, lumbar and sacral regions; understand the joints connecting the adjacent vertebrae Know the main features of a typical vertebrae and identify the atypical vertebrae Understand the movements of the vertebral column and how these changes with standing and age. Back problems are very common: estimated 80% of adult’s experience back pain at some point. NHS spend more than 1 billion a year on back pain related costs. Second largest cause of disability (arthritis/rheumatism being first) Structure: Vertebral column is made up of the neck, back (skull to coccyx). About 72-75cm in adults (height doesn’t matter: this comes from the femur trunk is relatively constant), ¼ of length is fibrocartilaginous IV discs. Contains 33 vertebrae (+/-1 in lumbar): reason why length is constant. Five regions: 7 cervical 12 thoracic 5 lumbar 5 sacral (fused) 4 coccygeal (fused) 1. Curves Movement between two adjacent vertebrae is small. However, if put together this forms a flexible yet rigid column. Adults contain four curves in the vertebral column: Cervical Thoracic Lumbar Sacral Kyphoses: (primary) concave anteriorly. Developed during fetal development: Thoracic kyphoses Sacral kyphoses (vertebrae fused) Lordoses: as we start to sit up, walk, move around secondary curves develop. They go in the opposite direction to the primary curve: concave posteriorly. More loose compared to primary. Cervical lordoses Lumbar lordoses Allows us to stand upright and see forward, allow for extra flexibility, give resilience (act as a shock absorber). These curves are dynamic: can increase/decrease curvature. This is done to protect the brain from being moved about in the skull. 2. Abnormal Curve Developmental anomalies or pathologic conditions (osteoporosis: where bone is lost). Excessive thoracic kyphosis (humpback) Most common cause is osteoporosis: loss of bone within vertebral body causes anterior part of vertebrae to collapse. Compensatory increase in the cervical lordoses so that the individual can still look forward (forms humpback) Sherman’s disease When you lose bone in osteoporosis: vertebrae become more of a wedge (rather square). Lordosis: hollow-back, sway back. Anterior rotation/tilt of pelvic produces increased lumbar curvature. Associated with weakened trunk muscles (can develop in late pregnancy or with obesity. Hip flexors pull pelvis in this anterior rotation. Weak erector spinae muscles: leads to this happening. Scoliosis: crooked, curved back. Abnormal lateral curvature, usually accompanied with rotation of the vertebrae. Most common deformity of vertebral column in pubertal girls. Can be hormonally linked, developmental defect (hemi-vertebrae), or can be due to asymmetric muscle strength. Though no one knows that the exact cause is (idiopathic) Severe rotation can restrict, abdominal organs. Corrected by surgery, brace. Usually affected in the thoracolumbar area. Flat back syndrome: decrease in curvature in the lumbar region. There is posterior tilt of the pelvis. Often associated with muscle instability (hamstrings tight: knees flexed, hip flexors weak). Seen in ankylosing spondylitis (autoimmune). 3. Types of Vertebrae Typical vertebrae: there are 22/24 movable features: same features. Contain: Vertebral body: weight bearing part. Gets bigger as you go down the vertebral column. L5 (last of lumbar vertebrae) biggest, robust body. Vertebral arch: red section. Left, right pedicles meet 2 broad, flat plates of bone (laminae posterior). In the center, it forms the vertebral foramen: forms spinal cord. Form protection of the spinal cord. Seven processes: muscles attachment, ligament attachment, articulation with vertebrae above and below. Spinous process: most posterior (can be palpated). First one that can be found at the base of the neck C7. 2X Transverse processes: muscles and ligaments 4X Articular processes: articulate with vertebrae above, below Two atypical: C1 and C2 Cervical vertebrae: skeleton of the neck: smallest of the 24 (7 of them) Distinguishing feature: foramen in the transverse processes: vertebral arteries (from subclavian). C1: no spinous process, has no vertebral body. C2 has “stolen” it. Forms a dens: pivot joint (makes it the strongest of the cervical bones): C1 rotates around C2. First ID: between C2 and C3. Thoracic vertebrae: costal facets: mark where the ribs are articulating with the thoracic vertebrae. Head: Contain one or more facets on each side of vertebral body: articulates with head of rib. Tubercle: Contain another facet on each transverse process of the superior 10 thoracic vertebrae. Vertical foramen is more rounded, smaller compared to cervical region. Spinous process much longer, points down to interlock with neck vertebrae Lumbar vertebrae: vertebral foramen looks small; however, it is not. Looks this way because of the large body. Also, contains a sturdy lamina. Most easily distinguishable feature: spinous process: more flat blade/much squarer compared to the other vertebrae. Sacrum: large triangular bone: 5 fused vertebrae. Coccyx: small triangular bone: 4 fused vertebrae 18. Intervertebral Discs and Functional Anatomy of the Neck Learning Objectives To describe the structure and function of the intervertebral discs To explain how the intervertebral discs and the facet joints interact to create a functional vertebral column 1. Joints between vertebral bodies Intervertebral discs: cartilaginous (symphysis) contain layers, designed for weight-bearing and strength. Acts as a shock absorbed as well as attaching adjacent vertebral bodies. Annulus fibrosus: outer fibrous part, concentric lamellae of fibrocartilage (~ 20 layers). Fibers orientated in slightly different direction: crisscross strength. Nucleus pulposus: gelatinous central mass: gives shock absorbency. Problem: it dries out as you age. IV discs cannot withstand same shocks and compression: can lead to back problems Composition of the intervertebral disc: 23 (24 if you count joint sacrum and coccyx). Increases in size as you go down: cervical (3mm), thoracic (5mm), lumbar (9-11mm). Disc separated from bone of vertebral body by thin hyaline cartilage layer (end plate: helps fibrocartilage attach to bone). Attachment: epiphyses of the vertebral body never ossify. Nucleus pulposus: rehydrates while sleeping over- night: makes you 1cm taller. This is then pushed down as you go throughout the day due to body weight. Herniated discs: Nucleus pulposus can push out (protrude) or can be completely extruded or sequestered. This can potentially irritate the nerve root that is passing out of the spinal cord. Tend to go posteriorly: anterior ligament is much broader and much stronger. L1-S1 is most common as there is most pressure here (can herniate left or right). Pressure when sitting/down: sitting down/standing up increases pressure so that the fluid is squeezed out of the disc. When lying down: the fluid is sucked in. Best position to sit down in is leaning backwards puts less pressure. Higher chance if you have subluxation: misalignment vertebrae. 2. Blood Supply to IV Discs (and degeneration) Reason why the nucleus pulposus degenerates is because it is avascular. Only the outer 1/3rd of the disc is vascularized (same for nerve supply). Nucleus pulposus: low in oxygen, glucose. Contains high lactic acid (lots of metabolites) which makes it difficult to move fluid in. Gets some nutrients: diffusion Calcification: of the end plates also occurs. Blocks of the blood supply which degenerates the IV disc. Makes the IVD more liable to break/tear, disc is not as resilient, loose height. Degenerative changes start in your twenties and worsen as you get older. 3. Facet Joints Zygapophysial joints: synovial joints (plane), gliding movements. Occur between in inferior and superior articular processes of adjacent vertebrae. In lordosis: sizes of intervertebral foramen (IF) are reduced which can affect the spinal nerves and therefore various regions. Common in lumbar region: size of spinal roots is very large (motor neurons to big muscles in the leg, innervate large areas of skin), bigger than is ideal. Small loss of IF: causes compression. 4. Ligaments of the vertebral column Anterior longitudinal ligament: strong broad fibrous band. Covers and connects anterolateral aspects of the vertebral bodies and IV discs. Extends from pelvic surface of sacrum to C1 and occipital bone. Limits extension and maintain stability. Also, protects intervertebral discs from herniating internally. Posterior longitudinal ligament: much narrower. Runs within vertebral canal. Herniating can happen on either side of this ligament (does not cover whole disc). Attached mainly to IV discs and not to the bone (the anterior ligament is). Does extend from C2 to sacrum. Well innervated. Ligamentum flava: attaches adjacent vertebrae. Rests vertebrae from separating. Are quite stretchy. High elastic content, so assists with straightening after flexion. Left and right LF on each side: gap. Interspinous ligaments: joints adjacent spinous processes. Much weaker: more like a weak membrane. Do help in keeping everything together. 5. Vertebral Movements Allowed by muscles: Paraspinals: numerous muscles (e.g. erector spinae): parallel to the spinal cord found on the left and on the right side. Only one that is different: quadrate lumborum: sideways movement. These paraspinals can go into spasm: they will shorten, and will reduce the size of the intervertebral foramen. This will compress and trap the nerve root as it exits. 19. Skeletal Muscle Learning Objectives Understand the structure of skeletal muscle fibre Understand the physiology of the skeletal muscle fibre Skeletal muscle is involved in movement, maintaining posture, stabilizing joints, generating heat. Makes up about 40% of your body weight, most abundant type of muscle. 1. Anatomy of Skeletal Muscle Nerve and blood supply: usually one nerve, artery and one or more veins (fits into a compartment). All enter or leave near the center of the muscle and then branch out. Connective tissue sheaths: individual muscle fibers and groups of muscle fibers as well as the whole muscle is wrapped by connective tissue. Endomysium: reticular fibers that hold, carries smallest capillaries Perimysium: a thick c.t. that surrounds groups of muscle fibers (fascicles) Epimysium: another layer of c.t. that organizes fascicles into muscles Attachments: most muscles cross a joint and attach to bones it at least two places Within muscle fibers itself: myofibrils. These are composed of sarcomeres which is the functional unit of the myofibril. Consists of the myofilaments of actin and myosin. Tendon will insert into the bone (insertion point) to join muscle onto bone. Tendon attached to fascicles, epimysium at the: Myotendinous junction: collagen fibers of tendons: continuous with c.t. of muscle C = collagen T1 F= fibroblast N = muscle myonuclei. Tendon bone attachment: at the other end of the tendon: insertion into the bone. Tendon uncalcified fibrocartilage calcified fibrocartilage bone. As the bones grow the attachment points also must move relative to the growth of the bone. Having (uncalcified) fibrocartilage allows movement of the attachment so it stays in the right location as we grow. 2. Microanatomy of a muscle fibre Various important terms: Sarcolemma: plasma membrane Multinucleate: fusion of many cells into one (muscle cells). Fusion of these cells form the long fibers of muscle: have many nuclei. Sarcoplasm: cytoplasm contains myoglobin to store oxygen Muscle proteins: arranged into sarcomeres. Actin, myosin (make up majority of sarcomere) Accessory proteins: titin (largest protein in body), dystrophin (largest gene), tropomyosin. NOTE: nuclei are pushed to the periphery in cross-section. Central nuclei: sign of damage. Satellite cell: stem cell population that always remains present. Sarcomere: have various banding Z-Lines: places where actin filaments are anchored M-lines: sites where myosin filaments are anchored A-bands: myosin filaments (darker bands) I-bands: lighter bands: only actin present H-bands: only myosin present. Actin and myosin are the contractile filaments. Myosin is a globular protein (contains globular head). Tropomyosin and troponin (calcium binding protein) are associated with actin: wraps around the actin filament and blocks binding site for myosin in the resting position. Troponin binds calcium which allows myosin to bind. Sarcoplasmic reticulum: modified smooth endoplasmic reticulum which acts as a store of calcium. T-tubule network: a pathway for the AP to travel from myotendinous joint to rest of muscle. These are extension of the plasma membrane that run deep into the muscle fibre. Two parts of sarcoplasmic reticulum with T-tubule in the middle triads. 3. Physiology of Skeletal Muscle Innervated by motor neurons. Motor neurons cell bodies all found in the spinal cord and brain Axons enters muscle and each axon branches to contact several muscle fibers (at the neuromuscular junction). General rule: one muscle fibre/one NMJ. Axon terminal: separated from muscle fibre by a 1-2nm synaptic cleft. Contains nicotinic receptor for Ach: activation causes AP in sarcolemma. Action potential travels down T-tubules: causes release of Ca2+ from sarcoplasmic reticulum into the sarcoplasm. Ca2+ binds to troponin: troponin pulls tropomyosin away from myosin binding site on the actin filament. Myosin head attaches to actin, pulls actin towards center of sarcomere. Ca2+ taken back into the sarcoplasmic reticulum, contraction stops. Energy (in the form of ATP) attaches to myosin heads. ATP ADP + Pi happens in the resting state when muscle is made ready for contraction. Can’t bind yet because of troponin. When myosin binding sites are open: neck ADP is released which allows head to pull the actin. Then returns to prestrike position. Motor unit: motor neuron and all muscle fibers supplied by it. If neuron fires: all muscle fibers innervated. The muscle spindle: mechanosensitive proprioceptors. Specialized muscle fibers that have wrapped around muscle fibers sense the stretch of muscle fibers. Detect changes in muscle length. 20. The Neuromuscular Junction Learning Objectives Know the anatomy, physiology and pharmacology relating to the neuromuscular junction 1. The Motor Unit Ventral horn of the spinal cord, exits via the ventral roots. Each alpha motor neuron (motor units to skeletal muscle) innervate one set of muscle fibers = motor unit. Neuromuscular junction: connection between motor nerve axon, skeletal muscle fibre. Terminal branches on muscle of axon end-plate. Within end-plate, individual axon branches swell up into presynaptic axon terminals or terminal boutons (each has a synapse). Features Lots of mitochondria. Synaptic vessels. Muscle membrane is extensively folded around bouton. Acetylcholine: chemical transmitter used at NMJ. Reason: can be broken down and inactively extremely rapidly by cholinesterase. Contains an acetyl group and a quaternary amine. In nerve terminal acetylcholine is made from choline and acetyl-CoA using cholineascetylase. Docking: In NMJ: proportion of vesicles are attached to presynaptic membrane. Involves interaction between proteins of vesicles and proteins of presynaptic membrane. Docked vesicles Ach. Release of transmitter triggered by entry of calcium ions into the presynaptic axon membrane. Done by voltage gated calcium channels. There are various types (L, N types). Important clinically: L-type channels found in the heart (smooth muscle): inhibited to reduce workload N-type channels are found on presynaptic terminals mediating transmitter release. Calcium levels: maintained in close levels. Total concertation is ~2.5 mmol/L in plasma. Maintained: Parathyroid hormone: dissolves bone, releases calcium into circulation Calcitonin: stimulates bone formation at expense of plasma calcium. Vesicle Life-cycle: in synaptic cleft, empty vesicles are bound by a protein called clathrin, moves them back into cytoplasm where they are refilled with ACh. Cholinergic Receptors: Nicotinic cholinergic receptors located on muscle membrane. NOT voltage sensitive, but ligand gated. Has two binding sites for acetylcholine. Receptor made up of 5 subunits. End-plate potential: depolarization of muscle. Very important reliable conversion of a signal. Force of contraction ~ the amount of action potentials send. Called one-to-one transmission. After binding to the receptors, the Ach is released from its binding site and reenters the synaptic cleft. It can then bind to acetylcholinesterase for inactivation and conversion back to choline. Choline is taken back up into the axon by uptake pumps. Ach released and terminated quickly. (!) Each stimulus releases ~10% docked vesicles, which are ~1% of total vesicles. 2. Pharmacology (NMJ Blockers) Botox: a protein released from anaerobic bacterium clostridium botulinus: paralyses muscles by blocking the docking. Toxin gets taken up by the empty vesicles instead of choline and stops SNARE proteins working. Synapse gradually runs out of vesicles. Conotoxins: blocks calcium channels presynaptically. Victims: die from paralysis as no Ach released. Curare: secretion of tree frog. It is a competitive antagonist of nicotinic receptors postsynaptically. It binds irreversibly with Ach receptors and stops Ach acting. Has a higher affinity than Ach. Active ingredient is tubocurarine: can’t twist so remains stuck in the receptor in the muscle. Nitrogen atoms in Ach bind to receptor. Succinylcholine: rapidly acting (paralysis disappears as soon as it is not infused). Binds to Ach receptor, allows the channel to open and the muscle to contract. However, doesn’t detach from the receptor so muscle stays depolarized and becomes unable to carry action potential. Called a depolarizing blocker. 3. Pharmacology (NMJ Stimulants) Anticholinesterase is a drug that blocks acetylcholinesterase: Ach not broken down, muscle cannot relax: synapse is hyperactive. Can be tamed to combat diseases where synapses are too weak (e.g. myasthenia gravis) neostigmine and physostigmine.