Flashcards in Musculoskeletal system Deck (76):
What is the musculoskeletal system composed of?
- bones of the skeleton.
- other connective tissues that support and bind tissues and organs together.
How are bones joined?
- Ligaments hold the ends of bones together at joints.
What are the properties of cartilage?
- firm connective tissue but more flexible than bones.
- insufficient rigidity to withstand gravity.
- does not contain blood vessels or nerves.
What is a ligament?
- Fibrous connective tissue that connects bones to other bones.
What is a tendon?
- A flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone.
What is a mesenchymal cell?
- Multipotent stromal cell which can differentiate into a variety of cell types including osteoblasts (bone cells), chondrocytes (cartilage cells), myocytes (muscle cells) and adipocytes (fat cells).
What are the properties of a fibroblast?
- Cell in connective tissue that produces collagen and other fibres.
- Synthesises the extracellular matrix and plays a role in wound healing.
What are the properties of connective tissue?
- Elastic, compressible, tough packing material.
What are the properties of cartilage?
- Turgidity, tensile strength, tough and resists deformation.
Properties of bone?
Hard, rigid, weight bearing, tensile strength
What are the four main types of biological tissue that support, connect or separate different types of tissues and organs in the body?
Give 2 examples of connective tissues?
- Tendons and ligaments.
Is cartilage slow or fast to repair?
What are the components of cartilage?
- Extracellular matrix: ground substance - GAGs and large proteoglycans complexed with collagen fibres. And fibres - type 2 collagen (hyaline cartilage), type 2 and type 1 collagen (fibrocartilidge) and type 2 collagen and elastic fibres (elastic cartilage).
- cells: chondroblasts (from perichondrium) - secrete matrix and chondrocytes - maintain matrix.
How is cartilage grown and maintained?
- the matrix is permeable to water and so dissolved oxygen and nutrients are delivered this way, as well as waste products removed.
- it's mainly non-vascular, therefore relies on diffusion via extracellular fluid.
- can grow by interstitial (within the matrix) as well as appositional (on surface) growth.
What are the three types of cartilage?
- Hyaline, fibrocartilidge and elastic cartilage.
How many types of cartilage?
Where is hyaline cartilage?
- Most common: articular surfaces (joints e.g. Knees and ankles), tracheal rings etc.
Where is fibrocartilidge?
- Found in the intervertebral discs and pubic symphysis.
What is the musculoskeletal system?
- Organ system that gives humans the ability to move using their muscular and skeletal systems.
- The musculoskeletal system provides form, support, stability and movement to the body.
Where is elastic cartilage?
- External ear, auditory canal and epiglottis etc.
How is cartilage repaired?
- No blood vessels in cartilage, nutrients to chondrocytes diffusing through the ground substance.
- Lack of blood vessels means that damage heals slowly or not at all.
- Lack of nerve supply means that damaged cartilage is painless although effect on neighbouring structures may cause pain.
What are the components of bone?
- extracellular matrix (ECM): consists of ground substance GAGs (osteocalcin and sialoprotein) and minerals (Ca++ PO4(2)- and hydroxyapatite) and fibres (type 1 collagen).
- bone cells (osteoprogenitor, osteoblasts, osteocytes and osteoclasts).
What are the four types of bone cells?
What is an osteoprogenitor cell?
- Mesenchymal stem cells that form osteoblasts (stem cells from periosteum).
What is an osteoblast?
- An immature bone cell that secretes organic components of the matrix (produce and maintain matrix).
What is an ostocyte?
- A mature bone cell that is formed from osteoblasts, they maintain the matrix and communicate via cell processes in canaliculi.
What is an osteoclast?
- Multinucleated macrophages acting as scavengers of unwanted material, remove matrix.
How is bone grown and maintained?
- It has a mineralized matrix impermeable to water and small molecules.
- It needs an intimate blood supply (key to structural organisation) and it grows by appositional growth only.
What is appositional growth?
- Process by which old bone that lines the medullary cavity is reabsorbed and new bone tissue is grown beneath the periosteum, increasing bone diameter.
What is compact bone?
- Dense bone organised into haversian systems.
- Forms the outer shell of all bone and also the shafts in long bones.
What is spongy bone?
- Bone organised into a 3D network of spicules with spaces.
- Found at the expanded heads of long bones and fills most irregular bones.
What are the two basic structural types of bone?
- Compact and spongy.
What is a bone canal?
- Within cortical bone, osteocytes give rise to vessels that run in canals. Haversian canals run longitudinally and volkmanns canals run radially.
- The blood supply is rich where there is bone marrow and at muscle attachments, generally the more muscle that covers a bone, the better its blood supply and ability to heal.
What is a Haversian canal?
- Series of microscopic tubes in the outermost region of bone called cortical bone that allows blood vessels and nerves to travel through them.
- Each canal generally contains one or two capillaries and nerve fibres. - These canals surround blood vessels and nerve cells throughout bones and communicate with bones cells through connections called canaliculi.
What is a volkmanns canal?
- Inside osteons (function unit of compact bone).
-Usually run at obtuse angles to the Haversian canals and contain anastromosing vessels between Haversian capillaries.
- Volkmanns canals are any of the small channels in the bone that transmit blood vessels from the periosteum into the bone and that communicate with the Haversian canals.
What is periosteum?
- A dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.
Why does bone need a blood supply?
- Because of the hard mineralised bone matrix, osteocytes can not be nourished by diffusion, and blood vessels are necessary.
What are the sources of arterial blood in bone?
- from periosteum at many sites.
- a large nutrient artery passes through nutrient foramen and supplies most of shaft. Some bones have several.
- ends of the long bones are supplied by metaphyseal and epiphyseal arteries, which arise from arteries that supply an associated joint.
What is ossification?
- The process in which cartilage is turned into bone.
- Bone grows in three stages, first tissue forms a mesh of collagen fibres, then the body creates a polysaccharide that acts like cement to hold the tissue together and finally calcium crystal salts are deposited to form bone.
What is intramembranous ossification?
- Essential process during fetal development in which bone tissue is created.
- Also essential process during the natural healing of bone fractures and the formation of bones of the head (and mouth I think).
- Cartilage is not present during this process.
- Bone is deposited by osteoblasts within primitive mesenchymal tissue. The bones of the vault of the skull, the clavicle, the maxilla and most of the mandible are formed this way.
What are the processes by which bone tissue are created during fetal development?
- Intramembranous ossification and endochondral ossification.
What is a bone island?
- A benign bone tumour mostly encountered as an incidental finding.
- They are round and small (2-20mm) intramedullary condensations composed of lamellar corticol bone.
What is endochondral ossification?
- Essential during fetal development, in which bone tissue is created.
- Cartilage is present during this process.
- Involved in formation of long bones, length of long bones and natural healing of bone fractures.
Model of endochondral ossification?
Fetal (cartilaginous model -> bone collar -> cartilage cells die -> primary centre blood vessels enter -> increase in length by interstitial growth of cartilage) -> childhood (secondary centres) -> adolescence (cartilaginous growth plate, growth in length possible, also wear point) -> adult (epiphyseal line, no growth possible).
What do they mean by bone remodelling?
- Bone is continually being remodelled by the activity of osteoblasts and osteoclasts.
- 3-5% of skeleton continuously replaced: new Haversian system takes 3-4 weeks.
- 5% compact bone replaced annually.
- 25% cancellous bone replaced annually.
What does bone store?
- Acts as a store for calcium in the body for plasma and tissues.
What is cessation of bone growth?
- Growth in length stops when epiphyses fuse.
- This occurs at different times for different bones.
- In girls, the menarche usually coincides with epiphyseal fusion, so oestrogen contraceptives may stunt growth if started too early.
What are some examples of abnormal cessation of bone growth?
- gigantism (too much growth hormone before epiphyseal fusion).
- acromegaly (large extremities - too much growth hormone after fusion).
- achondroplasia (hereditary defect of endochondral ossification in which long limb bones fuse early giving short limbs, while the trunk and skull develop normally).
- abuse (adolescent athletes who use growth hormone will find that it prolongs the life of the epiphyseal plate and delays the fusion of the ends of long bones not yet united, there may be joint problems later).
Explain secondary fracture repair?
Bleeding -> scar -> callus of hyaline cartilage (3weeks) -> emergency woven bone (4-5weeks) -> compact lamellar bone (months).
- Bone is replaced by bone while most other tissues are replaced by scar tissue.
What is callus?
- The bony healing tissue which forms around the ends of broken bone.
What are the factors influencing bone growth?
- mechanical factors.
- bone-derived growth factors?
What mechanical forces influence bone growth?
- shape of bone indicates function.
- cells must be able to respond to mechanical stress.
What are nutritional factors influencing bone growth?
- vitamin D (reduced calcification).
- vitamin C (collagen disrupted).
- vitamin A (endochondral growth reduced).
What hormones influence bone growth?
- growth hormone (growth plate increase).
- adrenal androgens (prepubertal growth spurt).
- gonadal steroids (closure of epiphyses).
- thyroxine (essential for osteogenesis).
- parathormone (Ca from bone to plasma).
- oestrogen (maintains bone density).
Which bone derived growth factors influence bone growth?
- BMPs (bone morphogenic protein).
What is osteoporosis?
- Loss of bone mass.
- Reduced weight bearing (wheelchair user).
- Reduced oestrogen (menopause).
- Reduced gravity (astronauts).
What is osteomalacia?
- Bone softening: vit D deficiency (poor calcification), rickets in children (permanent deformity).
What is Paget's disease?
- Control of resorption and formation uncoupled.
- Overgrowth of bone or reabsorbtion.
- Mosaic of over and under production.
- Bone produced is woven and therefore weak.
What is osteogenesis imperfecta?
- Brittle bones.
- Genetic defect in type 1 collagen and poor mineralisation.
Define mys, myo and sarx?
- Mys and myo = muscle and sarx = flesh.
What are the three types of muscle?
- striated/voluntary (skeletal e.g.muscles of movement).
- striated cardiac (rhythmic contraction).
- smooth/involuntary (e.g. Gut peristalsis and womb contraction).
Note: muscles don't push they only contract therefore often arranged in opposing groups or layers.
Characteristics of muscle?
- Myosin (thick) and actin (thin) filaments.
- Myosin bipolar therefore bidirectional movement, anchored at M line.
- Actin filaments (f actin) anchored at z line by alpha actin to actinin, z protein, filamin and amorphin.
Characteristics of skeletal muscle
- Myoblasts fuse to form: multinucleated muscle cells, peripheral nuclei, non branched fibres, striations.
- Skeletal muscle needs intricate blood supply and there is little regeneration (fibrous scar tissue).
What are muscle spindles?
- Specialised bundles which monitor muscle tensions.
How are joints moved?
- Joints are moved by the muscles spanning the joint.
How are joints classified?
- cartilaginous (primary and secondary (symphysis).
Joints are classified on the basis of structure.
What is a fibrous joint?
Bone - fibrous tissue - bone. Two bones bound together by fibrous tissue, e.g. Inferior tibiofibular joint and joints between bones of the skull vault.
- Fibrous joints permit little or no movement except that of fetal skull bones which move on each other before and during birth but during early childhood this becomes increasing restricted.
What is a cartilaginous joint?
- These allow more movement than fibrous joints.
- There are both primary and secondary cartilaginous joints.
What is a primary cartilaginous joint?
Bone - hyaline cartilage - bone. Bony tissue is separated by hyaline cartilage.
- The junction between the shaft and epiphysis of a long bone constitutes a primary cartilaginous joint, as does the chondrosternal joint of a rib.
- As the parts of a long bone fuse during childhood and adolescence these joints gradually disappear and in adult only a few remain most notably the joint between the rib and the sternum.
What is a secondary cartilaginous joint?
Allows more movement than fibrous joints. Also known as symphysis. Bone - hyaline cartilage - fibrocartilage - hyaline cartilage - bone.
- Here articular surfaces are each covered by hyaline cartilage and between them is a fibrocartilaginous disc.
- Found in the midline of the body and include the joints between neighbouring vertebral bones and pubis symphysis.
What is a synovial joint?
- permit much movement and include the shoulder, hip, knee and ankle joint.
- Bony articular surfaces are covered by hyaline cartilage.
- The joint capsule is attached to the articular margins, synovial membrane (synovium) covering all intracapsular, non-articular surfaces.
- synovium: specialised connective tissue that produces synovial fluid to lubricate the articular surfaces and nourish hyaline cartilage.
- 1 of Serous membrane of body: permits a surface to move another.
Name some diseases of joints?
- tuberculosis (can cause skeletal deformity).
- osteogenic sarcoma and other tumours.
- osteoarthritis - inflammatory disease of joints.
- rheumatoid arthritis .
- ankylosing spondylitis.
What is osteoarthritis?
- Disease of articular cartilage. In weight bearing joints (elderly) due to wear and tear.
- Articular cartilage worn away exposing underlying damaged bone.
- Tries to heal but forms lumps (osteophytes) around the articular margins.
- Reduces joint space.
- Symptoms joint pain and limited movement.
What is rheumatoid arthritis?
- Inflammatory disease of synovium causing pain and limitation of movement.
- Inflamed and swollen synovium may be trapped between articular surfaces.
- Results -> more inflammation and swelling, limited movement.