Musculoskeletal System PDF

The muscculo-skeletal system. MUSCULO-SKELETAL Muscles Skeleton ❖ Skeletal muscle ❖ Bones ❖ Tendons ❖ Joints ❖ Ligaments...

The muscculo-skeletal system. MUSCULO-SKELETAL Muscles Skeleton ❖ Skeletal muscle ❖ Bones ❖ Tendons ❖ Joints ❖ Ligaments ❖ Articulating cartilages ❖ Ligaments SKELETAL SYSTEM The skeletal system can be divided into 2 functional parts: (i) The axial skeleton (ii) The appendicular skeleton Axial skeleton: Includes the skull, vertebral column & thoracic cage Appendicular skeleton: The upper & lower limb bones including those forming the pectoral and pelvic girdle BONES Bone, a living tissue, is the most modified form of connective tissue that makes up most of the skeleton. They provide the following functions: Support for the body & its cavities. Protection of vital organs Mechanical basis for movement Storage of salts Supplier of new blood cells Bone tissue is highly specialised 1.Cells and Fibres (ORGANIC COMPONENT- 1/3) 2.Calcium salts (INORGANIC COMPONENT - 2/3) 1 gives bone its elasticity 2 gives bone its rigidity The cellular component of bones are represented by t hree types of specialized bone cells called OSTEOCYTES, OSTEOBLASTS AND OSTEOCLASTS CELLULAR COMPONENTS OSTEOBLASTS – lay down bone and forms the bone matrix - They deposit inorganic salts & osteoid in bone tissue OSTEOCYTE – mature bone cells - monitor & maintains the bone tissue OSTEOCLAST – reabsorbs bone (a process that continues lifelong) - They breakdown bone releasing calcium & phosphates BONE STRUCTURE Compact (cortical) bone – outer dense layer which gives bone its smooth, white & solid appearance. It is covered in dense CT called Periosteum (outer) and Endosteum on its inner surface.  Spongy (cancellous) bone – deep airy layer of bone which is highly vascularised Central canal – contains nerves, lymphatics & blood vessels Lamellae – Cylindrical plates of bone surrounding the central canal Lacunae– Little cavities between the lamellae which houses the osteocytes. CLASSIFICATION OF BONES Bones can be classified according to their: ❖ Location: i.e. axial or appendicular ❖ Shape ❖ Method of development (i.e. ossification) Classification by.. SHAPE Bones can be classified according to their shape as follows: I. Long bones II. Short bones III. Flat bones IV. Irregular bones V. Sesamoid bones I. LONG BONES ❑ They are tubular in shape ❑ They are composed mostly of compact bone which is thick in the shaft (cortex) & thinner in the extremities ❑ While the spongy bone and bony marrow fill the ends/extremities of the bones. Examples of long bones include the femur, humerus, ulna, tibia and clavicle ▪ A typical long bone consists of a long shaft (diaphysis) that extends into a neck (metaphysis) and head (epiphysis) on its proximal and distal ends ▪ It also features various markings and formations, such as: ✓ Sulcus – a shallow groove on the bone surface ✓ Condyle – rounded articular area ✓ Epicondyle – eminence superior to a condyle ✓ Crest – ridge of bone ✓ Facet – smooth, flat area, usually covered with cartilage ✓ Foramen – passage through a bone II. SHORT BONES ❑ They are roughly cuboid or round in shape, ❑ Contain a thin layer of compact bone surrounding the spongy bone ❑ Examples include the tarsal and carpal bones. III. FLAT BONES ❑ They are mostly thin, flattened and usually curved ❑ They contain two parallel layers of compact bones surrounding a layer of spongy bone Examples include most of the skull bones, scapula, sternum and sacrum IV. Irregular bone ❑ They do not fit into any of the other categories ❑ Generally, irregular bones contain foramina through which soft tissue and neurovascular structures pass Examples include the vertebrae, hip bone and some bones of the skull. VI. SESAMOID BONES ❑ are small, rounded unique types of bones that are embedded in muscle tendons where the tendon passes over a joint ❑ The largest sesamoid bone in the body is the patella, but several other smaller sesamoid bones can be found in the hand and foot, usually in close proximity to the joints. Examples include the patella, pisiform Classification by..METHOD OF FORMATION ❖ The process or development of bone tissue is called OSSIFICATION or OSTEOGENESIS ❖ It begins before birth (in utero) and is not complete until about the 21st year of life ❖ During the development of the foetus there are 3 germ layers present, namely; ENDODERM, MESODERM & ECTODERM ❖ During the foetal phase, mesenchyme develops from mesoderm & they form the embryonic skeleton > this is the site where ossification will occur ❖ And in some cases cartilaginous models develop from the mesenchyme skeleton ❖ Thereafter, osteoblasts converge on the ‘models’ to ignite the ossification process ❖ The mesenchymal and/or cartilaginous ‘models’ undergo either INTRAMEMBRANOUS OSSIFICATION OR ENDOCHONDRAL OSSIFICATION A. INTRAMEMBRANOUS OSSIFICATION ❖ Definition: Mesenchymal models of bone undergoes ossification without an intermediate cartilage model being formed ❖ Examples of these bones include some bones of the skull & clavicles ❖ Usually flat bones ❖ Ossification usually begins around the 6th to 8th week gestation period B. ENDOCHONDRAL OSSIFICATION ❖ Definition: Cartilaginous (hyaline) models of bone formed from mesenchyme undergoes ossification (also around 6th week gestation period) ❖ The model then ossifies starting in the centre of the shaft (the PRIMARY OSSIFICATION CENTRE –POC) @ 8th week gestation period ❖ Ossification proceeds proximally and distally, until by birth, the shaft is ossified while the extremities are cartilaginous  ❖ After birth, the extremities ossify (the SECONDARY OSSIFICATION CENTRE – POC) Examples of these bones include the rest of the skeleton (i.e. femur, hip, tarsals). Usually long, short, irregular bones BLOOD SUPPLY TO BONES There are four groups of vessels 1. PERIOSTEAL ARTERY 2. NUTRIENT ARTERY – supplies both the marrow and the greater part of the shaft, especially in children’s bones. There may be more than one. Its terminal branches (at the extremities) form an anastomoses with branches of metaphyseal arteries. 3. METHAPHYSEAL ARTERY 4. EPIPHYSIAL ARTERY HAEMATOPOIESIS ❖ The production of all of the cellular components of blood and blood plasma ❖ Occurs during embryonic development and throughout adulthood to produce and replenish the blood system. ❖ Most blood cells are produced within the marrow of the bone – there are 2 types: RED MARROW & YELLOW MARROW. Both contain blood vessels and veins that transport nutrients and waste in and out of bones ❖ Red marrow: responsible for blood cell production  ❖ Yellow marrow: is composed mostly of fat and resides in the hollow centres of long bones, such as thigh bones ❖ At birth = all marrow is red – produces more blood ❖ Adults = red and yellow marrow is equal ❖ Red marrow bones = spine, sternum, ribs, pelvis (high concentrations) ❖ Production: red blood cells = 200 billion; white blood cells = 10 billion; platelets = 400 billion each day CLINICAL: FRACTURE OF BONE ❖ A fracture is referred to as a breakage in bone due to injury/stress or disease ❖ There are a number of fractures that can occur, namely; simple, compound, comminute, incomplete CARTILAGE & JOINTS CARTILAGES ❖ Cartilage is a flexible connective tissue found in multiple organ systems of the body. ❖ It is composed of specialized cells called chondrocytes, collagen fibres & abundant ground substance rich in proteoglycan and elastin fibres. It can be classified into 3 different types: i) Hyaline cartilage – most abundant of the cartilages and is found in joints, as well as the nose, larynx, trachea and ribs ii) Elastic cartilage – is similar to hyaline but contains more elastic fibres. Eg: epiglottis ii)Fibro cartilage – is composed of collagen fibre type I and ground substance. Eg: intervertebral discs & pubic symphysis JOINTS Definition: a joint/articulation is a connection or union of 2 or more bones or cartilages The study of joints is known as ARTHROLOGY Joints can be classified into 3 different types: (i) Fibrous joints (ii) Cartilaginous joints (iii) Synovial joints I. FIBROUS JOINTS ▪ articulations in which the bones are connected by dense fibrous connective tissue ▪ The bones in fibrous joints are firmly held together so that the joint allow for little to no movement Examples: 1. Skull sutures - These gradually ossify from within outwards. Immovable. 1. Interosseous ligaments between forearm & leg bones. Some movement possible especially in forearm. II. CARTILAGINOUS JOINTS ▪ Articulations in which the bones are connected by cartilage. PRIMARY Union between bone & hyaline cartilage Found in all growing bones where shaft meets its epiphyseal (growth) plate – no movement possible Also found in ribs @ the costochondral joints.  SECONDARY Union between bones whose articular surfaces are covered with a thin layer of hyaline cartilage These hyaline laminae are united by fibro cartilage Frequently a cavity found in the fibro- cartilage is filled with tissue fluid, eg. Pubic symphysis Stern manubrial joint Intervertebral joint Limited movement possible CARTILAGINOUS JOINTS III. SYNOVIAL JOINTS ▪ Are freely mobile joints in which the bones are not in direct contact, but are separated by a potential space called the synovial cavity ▪ The synovial cavity is lined by a synovial membrane - secretes the synovial fluid which nourishes and lubricates the articulating surfaces in order to reduce friction ▪ The articulating bones in most synovial joints are lined with hyaline cartilage ▪ These joints usually have a wide range of motion, which is defined by the joint capsule, the supporting ligaments and muscles that cross the joint There are 6 different types of synovial joints: a. Hinge b. Pivot c. Ball and socket d. Ellipsoid/condyloid e. Gliding f. Saddle These joints all have their own range of movement HINGE JOINT The ‘c’ shaped surface of bone swings about the rounded surface of another - Movement: flexion or extension Example: elbow joint (humero-ulnar) BALL & SOCKET JOINT - The spherical end of one bone fits into a concave socket of another - All movement possible - Example: shoulder joint (gleno- humeral) ELLIPSOID JOINT - A reduced ball & socket arrangement. Where an oval surface of one bone fits into a concavity of another bone. - Movement: flexion, extension, abduction, adduction or circumduction (limited) - Example: wrist joint GLIDING JOINT - Opposed usually flat surfaces glide across each other. - Movement: limited to gliding - Examples: Sternoclavicular joints, inter-carpal joints PIVOT JOINT - The rounded part of one bone fits into the groove of another - Movement: uniaxial/rotation - Example: atlanto-axial, proximal radio-ulnar SADDLE JOINT - Concave surfaces of 2 bones articulate with each other (saddle shaped bones) - Movement: all except rotation - Example: carpometacarpal joints of thumb Hilton’s law: “the nerve supplying the joint also supply the muscles moving the joint & the skin covering the insertion of these muscles” MUSCULAR SYSTEM MUSCLES All physical function of the body involves muscular activity, and as muscles are responsible for all body movement they can be considered the ‘machines’ of the body (Marieb, 2013) Muscles provide several functions: MOTION – both obvious (e.g. walking) and not obvious (e.g. heart pumping) MAINTENANCE OF POSTURE – sitting and standing (stationary) PRODUCTION OF HEAT – up to 85% of all heat PROTECTION STABILITY of joints Muscle tissue constitutes about ½ ones body weight and consists of specialised cells with the following characteristics: 1. EXCITABILITY – Ability to receive & respond to stimuli 2. CONTRACTILITY- Ability to shorten, thicken or contract 3. EXTENSIBILITY – Ability to stretch or extend 4. ELASTICITY – Ability to return to its original shape TYPES OF MUSCLE TISSUE The body contains 3 different types of muscle tissue: ❑ Cardiac ❑ Skeletal ❑ Smooth I. SKELETAL MUSCLE ❖ Named for its location, skeletal muscle attaches to bone & moves the skeleton ❖ Striated – it has light & dark bands when viewed under a microscope ❖ Voluntary movement– under conscious control ❖ Accounts for approx. 40 – 50% of body weight in adults ENDOMYSIUM: a delicate CT sheath that surrounds each muscle fibre (cell) PERIMYSIUM:CT sheath surrounding groups of muscle fibres (fasciculus / li) EPIMYSIUM: surrounds a whole muscle which is composed of many fasciculi. This is closely associated with and sometimes fused to the DEEP FASCIA. It is these CT sheaths which convey nerves, lymphatics & (the essential) blood vessels to and from muscles. They are continuous at the muscle ends with its tendons. NAMING OF MUSCLES Muscles are classified or named according to: Shape – rhomboid, trapezius, quadratus femoris Location – tibialis posterior, tibialis anterior Number of heads – biceps, triceps, quadriceps Action – flexor carpi ulnaris NERVE SUPPLY OF MUSCLES Essential for muscle activity – if nerve is cut and unrepaired the muscle will atrophy It has both motor and sensory nerves that are derived from usually 2 consecutive spinal nerves NEUROVASCULAR SUPPLY – refers to the blood and nerve supply. Incl. venous & lymphatic drainage What do we mean by ORIGIN, INSERTION, ACTION AND NEUROVASCULAR SUPPLY of a muscle? ❑ The ORIGIN of a muscle refers to one end of a muscle, generally at the location where it attaches to a bone (also known as the proximal attachment) ❑ Muscle fibres help control the physical forces within the body. When they are grouped together, they facilitate movement of our limbs and tissues. ❑ Muscle contraction results in a range of movement and is known as the ACTION of that muscle. ❑ The INSERTION of a muscle is the place where one end of a muscle is attached to the freely moving bone of its joint OR to another bone (also known as the distal attachment) I. CARDIAC MUSCLE ❖ Found only in the heart. ❖ Involuntary movement & forms the walls of the heart (myocardium) ❖ Striated – it has light & dark bands when viewed under a microscope. ❖ Its main function is to propel blood into the circulation by making the right atrium contract. ❖ Cardiac muscle has a single nucleus – they are branched and tubular. I. SMOOTH MUSCLE ❖ Located in the walls of internal hollow organs & blood vessels. ❖ Examples: intestines, urinary bladder, ureters ❖ Involuntary muscle movement. Controlled by the medulla oblongata. ❖ Non-striated, has a single nucleus and are usually arranged in parallel lines