Skeletal System 2024.pptx

Photos: Katy Andrews, Body Worlds   Define the types, structure and function of bone  Understand the process of ossification Learning outcomes  Develop knowledge about tendons, ligaments, cartilage, joints, and muscles  Describe some...

Photos: Katy Andrews, Body Worlds   Define the types, structure and function of bone  Understand the process of ossification Learning outcomes  Develop knowledge about tendons, ligaments, cartilage, joints, and muscles  Describe some diseases linked with the skeletal system  The Skeletal System Composed of:  Bones  Tendons  Ligaments  Cartilage 20% of body mass!  Muscles  The Skeletal System Derived from the mesoderm germ layer Includes all bones, and also tendons, ligaments and cartilage that connects them Provides support to the body Protects internal organs and fragile body tissues Provides structure for muscles to attach so we can move Bone Tendon Ligament Cartilage Anatomical Directional Terms 6 Main Functions Types of Bones Bone types:  Bone Types 1. Long Bones: Longer than wide Consist Inner core ofof bone marrow- a tube & a variable contains nutrients and help in number formation of of ends cells Usually curved for strength E.g: Femur, Tibia, Fibula, Humerus, Ulna and Radius. 2. Short Bones: Bone Types Roughly cuboid shaped, or not much longer than wide E.g: Carpal and tarsal bones Cube shaped Provide strength & stability Subject to high forces  Bone Types 3. Flat Bones: Generally thin and plate-like in shape Provide shield-like protection For extensive protection Provide extensive surface for or provision of broad surfaces for muscular attachment muscle attachment E.g: Cranium, sternum, ribs, scapulae, iliac bones 4. Irregular Bones: Bone Types Complex structure E.g: Vertebrae, pelvis and some facial bones Many purposes e.g.: - protection of nervous tissue (vertebrae) - provide multiple muscle anchor points (sacrum) - maintain pharynx and trachea support and tongue attachment (hyoid bone)  Bone Types Bone embedded within tendon or muscle 5. Sesamoid Bones: Greek ‘sesame seed’ Act as pulleys, Small round or oval bones located in tendons providing smooth surface for tendons to Largest isDistal the patella portion –ofthe 1st knee cap slide over metacarpals  Bones Activity Using a partner, label some: - Long bones - Short bones - Flat bones - Irregular bones - Sesamoid bones Structure of bones  Bone Structure Cortical (Compact/Outer) Bone:  Makes up 80 % bone mass  Made up of osteons - columns of bone aligned in the same way as the applied force  Central canal of osteon contains nerves and blood vessels, linked by perforating canals. Cancellous (Spongy) Bone:  Lighter than compact bone to reduce overall bone weight  Spaces between trabeculae contain marrow  Long bone anatomy Diaphysis:  Shaft or body  Long, cylindrical, main portion Epiphyses:  Proximal or Distal end Metaphyses:  Region in mature bone where diaphysis joins epiphyses Articular Cartilage:  Thin layer of hyaline cartilage covering part of the epiphysis at bone to bone articulation points Periosteum:  Tough sheath of irregular connective tissue and blood vessels that cover the bone except at areas of articular cartilage Medullary Cavity:  Cylindrical cavity in the diaphysis containing marrow Endosteum:  Thin membrane covering the medullary cavity  Contains a single layer of bone-forming cells Detail of bone structure  Osteon – cells: Osteocytes: Mature blood cells that maintain bone matrix Osteoblasts: Bone constructors Osteoclasts: Bone breakers Osteoblasts and osteoclasts work together to keep regenerating bones (bone remodelling)  Osteon cell function  When an injury occurs, osteocytes release chemical signals that attract/direct osteoclasts to the site of damage  These secrete collagen digesting enzymes & acidic hydrogen ions to dissolve calcium phosphate from damaged bone  These molecules will be transferred to the blood via resorption  Osteoclasts undergo apoptosis – cell death, releasing molecules and hormones that attract osteoblasts, which rebuild the bone  Ossificati  At 6th/7th onbones (305 in week gestation: 206 new-born)  Cartilage becomes bone via osteogenesis / ossification  2 Pathways:  Intramembranous (flat bones)  Endochondral (long bones)  The mature bone structure is the same regardless of its formation pathway F Photo: Katy Andrews, Body Worlds o Berlin 2016 e t a l Intramembranous Ossification  Intramembranous = from a membrane  Ossification = production of bone  Before week 8 of foetal development  Mostly flat bones are formed using this pathway (e.g. cranial bones)  Intramembranous Ossification 1. Ossification Centre Development: Mesenchymal cells differentiate into osteoblasts and group into ossification centres. Osteoid is the unmineralized part of the bone matrix.  Intramembranous Ossification 2. Calcification: Osteoblasts are trapped by the osteoid and become osteocytes. Osteoid becomes calcified.  Intramembranous Ossification 3. Trabeculae Formation: Extracellular formation, develops into trabeculae that fuse to form spongy bone, with blood vessels growing in the spaces between = red marrow.  Intramembranous Ossification 4. Periosteum Development: Mesenchyme condenses at the periphery = periosteum. Eventually a thin layer of compact bone replaces the spongy bone at the surface.  Endochondral Ossification Process by which embryonic cartilage becomes ossified  Endochondral ossification – summary: 1. Cartilage Model Development: Chondroblasts develop from mesenchymal cells and secrete cartilage extracellular matrix, forming a cartilage model. 2.Cartilage Model Growth: Chondroblasts become chondrocytes, embedded in extracellular matrix. Chondrocytes calcify, some die forming cavities. Blood vessels move in. 3.Primary Ossification Centre: Osteoblasts move in to the primary ossification centre in the diaphysis, and calcify the cartilage. 4.Medullary Cavity Development: The primary ossification centre growth moves towards the bone ends. Osteoclasts break down the trabeculae, forming the medullary cavity in the diaphysis. 5.Secondary Ossification centres: Occur around birth when blood vessels enter the epiphyses. Ossification precedes outwards. 6.Formation of Articular Cartilage & the Epiphyseal Plate: Hyaline cartilage covering the epiphysis becomes the articular cartilage. Hyaline cartilage between the diaphysis and epiphysis is responsible for lengthwise growth.  Bone Cells - Summary 1. Osteogenic Cells:  Unspecialised stem cells derived from mesenchyme  The only bone cells to undergo division into osteoblasts 2. Osteoblasts:  Synthesise & secrete collagen fibres and organic compounds  Build the extracellular matrix, becoming trapped in their secretions, become osteocytes 3. Osteocytes:  Mature bone cells. Maintain bone metabolism i.e. nutrient/waste exchange with blood 4. Osteoclasts:  Large cells derived from the fusion of white blood cells  Release lysosomal enzymes & acids that digest proteins & minerals in bone Break!  Tendons  Connect muscle to bone, providing stability during movement  Play role in positioning of limbs and act as springs to make movement more efficient  Strong to endure forces of muscle contraction  Tough band of connective tissue  Made of parallel collagen fibres- tensile strength  Ligaments  Connect bone to bone, shock absorbers  Some ligaments limit the mobility of articulations or prevent certain movements altogether.  Ligaments are viscoelastic. They gradually strain when under tension and return to their original shape when the tension is removed.  However, they cannot retain their original shape when extended past a certain point or for a prolonged period.  Hypermobility refers to people with more-elastic ligaments, allowing their joints to stretch further.  Cartilage  Flexible connective tissue Includes joints between bones, rib cage, tubes of bronchi, nose, intervertebral discs Not as hard/rigid as bone but stiffer and less flexible than muscle  It is part of a joint where two bones meet and allows movement to occur, also acting as a shock-absorber  3 types:  Hyaline e.g. shoulder joint or ribs Elastic e.g. external ear Fibrocartilage e.g. intervertebral discs Cartilage: Hyaline Elastic Fibrous  Joints  The place where two (or more) bones meet  The human body contains more joints than bones!  They are mainly responsible for movement: muscles contract across joints resulting in the movement of bones = movement of body  Functional classification of Joints  Non-moving joints known as Synarthroses.  Partly moving joints known as Amphiarthroses.  Fully moving joint known as Diarthroses.  Structural classification of Joints  Fibrous joints  Connect bones with fibrous connective tissue (collagen)  Do not move  Cartilaginous joints  Unite bones using cartilage  Do not move too much  Synovial joints  Freely moving joints Ball and Socket Joint Allows the distal bone to move in almost any direction E.g. In shoulder and hip  Hinge Joint Allows for bending and straightening motions in only 1 direction E.g. Elbow and knee  Pivot joint Rounded portion of bone enclosed within a ring of another bone E.g. In the neck (C1 and C2) Allows you to turn head side to side  Saddle Joint  Where one of the bones forming the joint is shaped like a saddle with the other bone resting on it like a rider on a horse.  Both bones are concave on one side and convex on the other.  Provide stability to the bones while providing more flexibility than a hinge or gliding joint. The bone sitting on the saddle can move in an oval shape relative to the other bone. E.g. thumb  Condylar Joint Permits movement in two planes, allowing flexion and extension in one plane and adduction and abduction in another. E.g. wrist, ankle Structure of a Joint  Bone surfaces are covered with cartilage.  The joint is surrounded by an articular capsule  The synovial membrane lines the entire joint except the articular surfaces  Joint cavity filled with synovial fluid Vertebral Column  ‘Backbone’ or ‘spine’  24 articulating vertebrae, 9 fused vertebrae  Named according to their region of the spine  Separated by intervertebral discs  Forms spinal canal that houses spinal cord  Vertebral column functions  Protection – encloses and protects the spinal cord within the spinal canal.  Support – carries the weight of the body above the pelvis.  Axis – forms the central axis of the body.  Movement – has roles in both posture and movement.  Vertebr ae Each vertebra consists of - Anterior vertebral body (weight bearing), those lower in the spine are larger Posterior vertebral arch forms the enclosed hole (vertebral foramen), these line up to house the spinal cord  Facet joints between the arches are lined with cartilage  The vertebral discs separate the individual vertebral bones  Vertebra- common structure The upper and lower surfaces of the body of the vertebra are flattened and rough in order to give attachment to the intervertebral discs Side walls of spinal canal Form intervertebral foramen- Space that spinal nerves branch out Attaches muscles and ligaments The laminae give attachment to the ligaments that  Vertebral specialisations The size of vertebrae varies according to placement, spinal loading, posture (and pathology) Along the length of the vertebral column the vertebrae change to accommodate different needs related to stress and mobility Cervical  Support only the head so have a relatively small body spinal cord is thickest near the point where it meets the brain, so vertebral canal is much wider  the spinous process is bifurcated (notched)  transverse foramen that serve as passageways for the vertebral arteries and veins that supply blood to the brain  articulations between adjacent cervical vertebrae permit more flexibility - the neck is more flexible with more range of motion than the torso  C1 is called the atlas C2 is called the axis C7 is called the Thoracic  The vertebral bodies are roughly heart-shaped and are wide  The thoracic vertebrae attach to ribs and so have articular facets specific to them.  As they progress down the spine they increase in size to match up with the adjoining lumbar section. Lumbar  vertebral body is quite large (thick and oval in shape) as the lumbar vertebrae must support a large amount of weight  spinous process is short and thick  They allow significant flexion, extension and moderate lateral flexion Sacral/coccyx Sacrum  one bone formed from 5 sacral vertebrae that begin to fuse together aged 16-18  attachment site for muscles involved in the movement of the thigh  protects reproductive, excretory, and digestive organs  attaches the pelvic girdle to the axial skeleton  Sacral foramen openings between the fused sacral vertebrae transmitting the sacral nerves. Coccyx  formed from three, four, or five small or incomplete vertebrae Thoracic Sacrum Coccyx Cervical Lumbar  Intervertebral Discs An intervertebral disc lies between adjacent vertebrae in the vertebral column Each disc forms a fibrocartilaginous joint Allow slight movement of the vertebrae Act as a ligament to hold the vertebrae together Function as a shock absorber for the spine Made of a fibrous outer ring, containing a gel like substance made up of collagens I and II  Why has my Nan shrunk? 5ft 4” 5ft 1” Aged 19 Aged 92 Why do you  Intervertebral discs: shock absorbers shrink as  One effect of ageing and disc degeneration is that you age? the nucleus pulposus begins to dehydrate, thus limiting the ability of the disc to absorb shock.  Partly responsible for decrease in height with age  Slipped/ Herniate d Discs A slipped disc occurs when the outer case of the disc splits, resulting in the gel inside bulging out of the disc. The damaged disc can put pressure on the whole spinal cord or on a single nerve root (where a nerve leaves the spinal cord). This means a slipped disc can cause pain both in the area of the protruding disc and in the area of the body controlled by the nerve that the disc is pressing  Diseases of the skeletal system Arthritis - osteoarthritis and rheumatoid most common Cartilage between bones Autoimmune disease in which the body's gradually erodes, causing bone in immune system targets affected joints. the joints to rub together. Onset 20-40 years Much later age of onset Usually symmetrical Unilateral, may limit to one set of joints  Other Diseases of the Skeletal System Gout: A type of arthritis where crystals of sodium urate form inside and around joints Osteoporosis: loss of bone density, weakens bone making Photos: Katy Andrews, Body Worlds Berlin 2016 them more fragile and likely to break Rickets: Bones become soft and weak, often as a result of Vit D deficiency Ankylosing spondylitis: An arthritis condition in which there is inflammation of the spine (Top photos) Scoliosis: Curvature of the  Curvature- Disorder of the spinal column  Lordosis: Also called swayback, the spine of a person with lordosis curves significantly inward at the lower back.  Kyphosis: Kyphosis is characterised by an abnormally rounded upper back (more than 50 degrees of curvature).  Scoliosis: A person with scoliosis has a sideways curve to their spine. The curve is often S-shaped or C- shaped.  Congenital Neuromuscular Scoliosis Degenerative Idiopathic causes Richard III The muscular system  Muscles are made up of bundles of myofibrils containing Bundles of muscle actin and myosin fibres are called fascicles Fascicles may be:  arranged in parallel e.g. biceps  convergent e.g. pectoralis  at an angle to the tendon, or pennate  The (more or less) fixed end of the muscle is the origin  The moving end of the muscle is called the insertion  Muscular dystrophies  Progressive breakdown of muscle with increasing weakness  Around 30 different types  Duchenne muscular dystrophy most common, accounts for ~ 50% of cases  Almost always genetic, usually affects males Innervation of muscles Innervation of the arm – the brachial plexus Brachial plexus injuries – Erb’s palsy Waiter’s tip  Diseases of motor nerves Motor neurone disease A neuro-degenerative disorder that leads to muscle weakness and wasting. Amyotrophic lateral sclerosis is the most common form. Myasthenia gravis An auto-immune disease of the neuromuscular junction that leads to weakness. Can be treated with drugs that  Short break before the practical. Make sure you have your lab coats!  Rat Dissection Identify organs and compare comparative positioning & size to human anatomy https://www.biologycorner.com/worksh eets/rat_dissection.html  Expose the muscles use scissors and forceps to gently lift the Skinni skin away Avoid the genital ng areas  Head and Neck 1. Locate the salivary glands, which on the sides of the neck, between muscles and the external layer of skin. You should not have to cut very deep. Peel the skin back to expose the salivary glands. They are soft spongy tissue that secrete saliva and amylase (an enzyme that helps break down food). The texture of these glands resembles chewing gum. 2. There are three salivary glands - the sublingual (yellow pin), submaxillary (green pin), and parotid (red pin). The parotid is easiest to find, it lies just beneath the ear and extends to the neck. See if you can find the others also. 3. Find the lymph glands which lie anterior to the salivary glands. Lymph glands are dark and circular and are pressed against the jaw muscles 4. Ease away the muscles of the neck to reveal the trachea. The trachea is identifiable by its ringed cartilage which provides support. The oesophagus lies behind the trachea,  Thor 1. ax Locate the diaphragm and the heart is centrally located in the thoracic cavity. The thymus gland, may be visible at the upper part of the heart. 2. The lungs are spongy organs that lie on either side of the heart and should take up most of the thoracic cavity. They lie closer to the back of the rat, you will need to push the ribs to the side to find them. 3. A sheet of muscle can be found just under the heart (and above the liver) - this is the diaphragm. This muscle is only found in Digestive system  Urogenit al 1. Syste The primary organs of the excretory system are the m kidneys. These organs are large bean shaped structures located toward the back of the abdominal cavity on either side of the spine. Renal arteries and veins supply the kidneys with blood. 2. Locate the delicate ureters that attach to the kidney and lead to the bladder. Wiggle the kidneys to help locate these tiny tubes. 3. Remove a single kidney (without damaging the other organs) and dissect it by cutting it longitudinally. Locate the cortex (the outer area) and the medulla (the inner area).  Sexi ng Male Female  Bone PullExposure muscle away to expose bones.  Compa re the Organs Remove all the organs in the body. Spread them out. Notice the different shapes and sizes.