Anatomy Flashcards
Vasovasorum
The capillaries around big arteries because they need their own blood supply
Two kinds of arteries
Elastic- lot of elastin and muscular
Two biggest veins in the body
Superior and inferior vena cava
Structures of the skeletal system
Bone, cartilage: precursor to most bones, also covers most mature joints, ligaments: holds bones together at joins, tendons : attaches muscle to bone
Axial vs appendicular skeleton
Axial: skull, vertebrae, ribs, sternum, hyoid
Appendicular: bone of the limbs, including pectoral and pelvic girdle
Function of skeletal system
- Support: structural integrity of the body, muscles, other tissues (e.g., teeth)
- Protection: of brain, spinal cord, heart, lungs
- Movement: muscle action on bones and joints enable limb actions, breathing, etc.
- Blood formation- red bone marrow is the chief producer of blood cells
- Mineral storage: body’s calcium and phosphorous.
- Comprises 1/3 collagen fibres (organic) and 2/3 inorganic hydroxyapatite (calcium and phosphate regulation/storage)
- hydroxyapatite= provides strength, collagen= provides flexibility
- adaptability through re-modelling
Components of the bone.
- Cortical (compact) bone: outer shell of the bone
- Trabecular/cancellous (spongy) bone: underneath joint surfaces
- Medullary (marrow) cavity: space in the diaphysis of a long bone that contain bone marrow
- Periosteum: external connective tissue membrane
- Endosteum: internal connective tissue membrane
Different types of bones
-Long bone: tubular in shape, longer>wide, shaft with marrow cavity -rigid levers acted upon by muscles.
E.g., clavicle, humerus, radius, ulna, metacarpals, femur, tibia, fibula, metatarsals, phalanges
-Short bone: tarsals, carpals
-Flat bones: frontal bone, parietal bone, sternum, scapula, ribs
-Irregular bones: sphenoid, temporal, lumbar vertebrae
-Sesamoid bones: patella
Bone features in a long bone
Diaphysis (shaft): cylinder of cortical bone
Epiphysis: rounded ends of a long bone
Metaphysics: neck of the long bone (contains the growth plate)
Articulate cartilage: hyaline cartilage that covers the joint surface
Bone joints and their classification
Joint (articulation): any point where two bones meet
- Bony: Synotosis (bony joint)
- Fibrous: Gomphoses, Syndemoses, Sutures
- Cartilaginous
- Synovial joints
Bony joint
Synotosis (bony joint): immovable joined formed when the gap between two bones ossified, effectively forming a single bone.
E.g.,
Fusion of frontal and mandibular bones
Fusion of first rib and sternum with old age
Fibrous joint
Synarthrosis (fibrous joint)- bones united by fibrous tissue (dense regular connective tissue). Little to no movement occurs at these joints, depending on the length of the fibres uniting the bones.
Three types of synathroses: gomphoses, syndesmoses, sutures.
Gomphoses- the tooth in the cavity.
Syndesmosis: fibrous joint where two bones are bound by long collagenous fibres fibrous membrane or cord) e.g., interosseous membrane, these joints are more mobile than gomphoses( but still minimal)
Sutures- immovable or slightly movable fibrous joints that closely bind the bones of the skull to each other.
Cartilaginous joints
Two bones linked by cartilage (slightly movable joints)
- Synchondrosis- bones are bound by hyaline cartilage, may ossify to synostosis (bony joint)
- Symphases- two bones joined by fibrocartilage, generally located in the midline of the body (slight motion), e.g., intervertebral discs, pubic symphysis
Synovial joints
Synovial joints (diarthroses): provide free movement between the bones they join. Five distinguishing characteristics:
- Joint (articular) capsule- unites the bones, spans and encloses the articular cavity and retains the fluid. Comprises the fibrous capsule and synovial membrane. - Joint (articular) cavity- separates articular surfaces, contains a small amount of lubricating synovial fluid. - Synovial fluid- joint lubricating fluid, lubricates surfaces, removes wastes, absorbs shock, distributes stress across articular surfaces - Articular cartilage- hyaline cartilage that covers the articulating surfaces - Reinforced by ligaments- extrinsic and intrinsic to the joint capsule.
Osteoarthritis
- Wear and tear arthritis
- Heavy use of synovial joints over time can cause degenerative changes: articular cartilage softens, degenerates and can wear away. Bone spurs can develop on exposed bone tissue.
- Causes considerable pain and joint deformation
- Normally a slow process, affects mostly weight-bearing used joints.
Bone development (two ways of ossification)
- Bone development begins at week 8 and finishes at ~25 years.
- Ossification can occur in two ways:
Intramembranous: direct mineralisation of connective tissue. Grows radially from a primary ossification centre (mesenchyme-NO cartilage) e.g., flat bones of face and skull, mandible and clavicle
Endochondral:
- cartilaginous template made from the mesenchyme
- continuously growing cartilage which is progressively replaced by bone
- different ossification centres emerge: primary in diaphysis, secondary in epiphysis
- epiphyseal plate ((growth plate) exists between diaphysis and epiphysis, e.g., all other bones in the body
Osteon/Harvesian system in compact bone
- Aligned parallel to long axis
- Osteon- concentric rings (lamellar) surrounding central Haversian canal
- Formed by osteoclastic tunnelling, which forms channel, then lines internally by osteoblasts, which are then entrapped.
- Osteocytes in lacunae become arranged in concentric rings.
Micro anatomy: bone cells:
Osteoblasts: deposit collagen and bone matrix called osteoid, lines endosteum
Osteocytes: Osteoblasts tapped in formed bone, Communicate through small channels called canaliculi, in cortical bone
Osteoclasts: Reabsorbs bone tissue for remodelling and to free calcium to the blood stream. Found in Howship Lacunae (reabsorption bay) Secretes organic acids to dissolve mineral component of bone; enzymes to destroy organic osteoid matrix, responds to growth, mechanical stress and blood calcium homeostasis.
Components of the Vascular System
Heart
Arteries
Veins
Aorta branches
Aorta-major artery from heart
Major branches of aorta: -brachiocephalic artery, subclavian, carotid artery
Five classes of blood vessels
Arteries, Arterioles, veins, Venules, capillaries
Microscopic Structure of Blood Vessels
- Tunica interna: -innermost layer -a single layer of squamous (flat) epithelial cells: endothelium -rest on basement membrane -BM a layer of connective tissue, made of elastin and collagen; anchor tunica intima to tunica media
Function: Endothelium regulates blood flow, prevents clotting. Produces chemicals (nitric oxide) to help regulate blood flow by relaxing smooth muscle in walls of blood vessels. Smooth lining in direct contact with blood offers little or no resistance to blood flow. - Tunica Media: -middle layer -forms most of arterial vessel wall - composed of moth muscle fibres, elastin. Activated sympathetic nervous system acts here and can stimulate smooth muscle fibres to contract, causing blood vessel to narrow (vasoconstriction). When the opposite happens, blood vessels increase in diameter (vasodilation) and blood flow increase.
- Tunica Externa: -outer layer -mainly has connective tissue fibres -supports blood vessels, connects them to surrounding tissues -larger blood vessels, small arteries, ‘vasa vasorum’ supply blood, nutrients to tunica externa, and tunica media.
Elastic arteries
Elastic arteries (conducting) Largest (1-2.5cm in diameter) Structural features: -large amounts of elastin -smooth muscle -large lumen with low resistance to blood flow -expand, recoil to accommodate changes in blood volume.
Muscular arteries
Muscular arteries (distribution)
0.25mm-1cm in diameter
-regulates local blood flow -deliver blood to individual organs
Structural: -possesses more smooth muscle but less elastin than elastic arteries
Arterioles
Smallest arteries (0.01-0.3mm in diameter) Structural Features: • All three vascular layers (tunic intimate, media and external) • When they are close to the capillaries have single layer of smooth muscle overlying endothelial cells • Blood flow form arterioles into capillaries is determined by diameter of arterioles.
Venules
• 8-10u in diameter
• Largest ones- Thin tunica externa and a tunic media compromising two or three laters of smooth muscle cells
• Venules join to for veins- Tunica externa consists of thick collagenous bundles.
• Largest veins
• Large tunica externa, thickened by smooth muscle
-superior vena cava
-inferior vena cava
Capillaries
• Arteries divide into arterioles which in turn divide into capillaries
• Capillaries, connect arterioles to venules
• Venules, connect to larger veins
• Largest veins are superior or inferior vena cava
Function of capillaries:
• Act as semipermeable membranes
• Allow diffusion of gases
• Transfer of nutrients, waste products
Structure capillaries
• Single layer of flattened endothelial cells of capillaries (exchange of substances)
• Capillaries- small slits in endothelial cells known as ‘pores or fenestrations’
- gases such as CO2 and O2, metabolic waste products can transfer
• Pores or fenestrations, slits are smaller than proteins
-prevent capillaries from losing vital substances (plasma proteins)
Types of capillaries:
- Continuous: nervous system and muscle
- Fenestrated:glomerular and gut mucosa
- Sinusoidal/Discontinuous: liver and marrow.
Exchange across capillaries
• Fluid movement through capillary wall as is governed by hydrostatic pressure
• Blood exerts pressure (BP) on capillary wall
-highest at arterial end, lowest at venous end
• Pressure causes fluid to move out through capillary pores into tissues
-Size of pores in capillary determines which nutrients will deliver to tissue.
Types of receptors in Vessels
Baroreceptors, chemoreceptors that maintain blood pressure and vital perfusion of organs.
Embryological origin of skeletal muscle
- At 9 weeks, first neuromuscular junctions appear on newly created myotubes.
- Soon myotubes receive first impulse from neutrons
- Originally myotubes are innervation is polyneural-lots of nerve fibres serving one muscle which then progresses to be mono neural after birth
- Only after birth superfluous connection are withdrawn and muscles innervation becomes mono neural.
Key features of skeletal muscle
- striated (contractile proteins)
- multinucleated
- organised as contractile units (sarcomeres)
Sarcolemma
Outer membrane of a muscle cell
Sarcoplasm
Cytoplasm of a muscle cell
Sarcoplasmic reticulum (SR)
Smooth endoplasmic reticulum of a muscle cell
Sarcomere
Smallest functional unit
Organisation of the muscle
Muscle -> Fasicle (bundle of muscle fibres) -> A single muscle cell/fibre (collection of myofibrils)-> A collection of myofilaments (myofibril) -> Sarcomere (Z line, A line, M band, actin, myosin)
Anatomy of Action Potential in Skeletal muscle
Triad ( T cistern are- T tubule- T cistern are): a structure formed by the T tubule with a sarcoplasmic reticulum (SR)- T cisternae
- T tubules run perpendicular to long axis of muscle
- Triads typically located at A-I junction in a sarcomere.
Innervation of Skeletal muscle
Neuromuscular Junction
• Chemical synapse b/w motor neurone and a muscle fibre
• Allows motor neuron to transmit nerve impulse to a muscle fibre-muscle contraction
Muscles require innervation to remain functional- contract or just maintain tone)- atrophy (waste away as a result of degeneration of cells due to no nerve supply or lack of movement)
Gross Anatomy of Skeletal muscle
Three connective tissue covering:
• Epimysium: encloses entire muscle
• Permimysium: surrounds fascicle (i.e., of muscle fibres)
• Endomysium: surround individual muscle fibre (within a fascicle)
(Fascia and role of fascia) (Myotendinous junctions)
Locations and functions of a skeletal muscle
-locomotion -support -postural
E.g., chest wall (pectoral is major, deltoid, serratus anterior)
Gross Anatomical Description of Sekeletal muscle
Origin, insertion, action, function, innervation of nerve supply.
Anatomical grouping of skeletal muscle (movement)
Agonists, antagonists, synergistic/stabilisers
Skeletal muscle contractions
- Concentric: shortening
- Eccentric-lengthening
- Isometric
Different kinds of skeletal muscle
-flat -strap -pinnate/multipennate -fusiform -quadrate -circular
Features of cardiac muscles
Striated and organised into sarcomeres, mono/binucleated, fibres shorter than skeletal muscle fibres, extensively branched- connected by intercalated discs
Location and feature of cardiac muscle
Location: heart
Function: coordinated contractions of heart-pumps blood into circulatory system
Features of intercalated discs in cardiac muscle
• Gap junctions: electrical coupling
• Desmosomes: anchorage with adjacent cells
• Zona-Adherens-type junctions
-anchorage with adjacent cells
-anchor actin filaments
Acts as Z discs; muscle cells meet end to end.
Purkinje fibres
Specialised cardiac myotubes
Beneath endocardium:
-large muscle cells:abundant glycogen
-sparse myofilaments, extensive gap junctions
-conduct- rapid than cardiac muscle fibres (synchronous contraction)
Features of cardiac muscle
- higher number of mitochondria-high metabolic demand
- T tubules- invagination of sarcolemma (reside over Z line of sarcomeres)
- T tubules and SR cardiac muscle form a ‘Diad’ (single T-tubule paired with terminal cistern of SR
- Role in action potential.
Features of smooth muscle
-no striations
-mononucleated
-shorted than skeletal muscle fibres
-random arrangement of the contractile protein units
-location: walls of hollow organs- urinary bladder, uterus, stomach, intestines, arteries.
-function: involuntary control via the autonomic system
E.g., eyes, lens, skin
Modified smooth muscle cells
Myoepithelial cells
- Stellate cells around secretory parts of exocrine gland
- Assistant secretions into secretory ducts, e.g., sweat, salivary and mammary glands
- ocular iris contract to dilate pupil
Myofibroblasts
-produce collagenous matrix but also contract at sites of wound healing
Myoid cells:
-Surrounds seminiferous tubules, contraction helps move sperm towards efferent ducts.
Difference between radiologist and radiographer
Radiologist: a consultant who interprets medical images across a range of modalities. May also run clinics, undertake biopsies and interventional radiology techniques. Many specialise, e.g., orthopaedic, neurology, cardiac, paediatric
Radiographer: -allied healthcare professionals, employ a range of techniques to produce high quality images to diagnose an injury or disease. Responsible for providing safe and accurate imaging examinations and often also the resultant report.
Ionising vs non ionising radiation
Ionising: Removes electrons from atoms
Includes X rays, Gamma rays and some UV
Non ionising: Sound waves in ultrasound, Radio waves in MRI
Radiography
Strengths: -great spatial resolutions- especially bone
-cheap and available
Weaknesses: -2D only -ionising radiation -very limited soft tissue visualisation
Mode of action X Ray: -Most of the X Ray photons are absorbed by filtration (due to low energy). X-Ray beam interacts with the patient over a restricted area. Photons will be: absorbed- lose energy and not reach the image receptor :transmitted- pass through patient and not interact with tissues :scattered- deflected from original path. Radiation reaching the receptor is then captured and made into a digital image.
Chest X Ray- 4 tissue densities: air, fat, soft tissue/fluid, bone.
Fluoroscopy
• Real time examination using continuous production of X Rays • Includes: -Ba examinations -Angiography -Cardiac procedures e.g., stents -Use of a C arm in theatre -Urology procedures.
Computer tomography
Strengths: • Cross sectional • Spatial resolution • Widely available Weaknesses • Ionising radiation • Limited soft tissue contrast
Modern CT scanners:
• Helical or spiral acquisition of images
• Patients moves through a rotating X Ray beam and set of detectors
• Creates 3D data which can be reconstructed
• Allows for complete scan in a single breath hold.
Scan times are very short.
Ultrasound
Strengths: • Non ionising radiation • Multiplayer • Dynamic • Doppler Weaknesses: • Operator dependent • Can’t see through bone or gas. Functions: • Obstetric and gynaecology referrals • Abdominal scanning- liver, kidneys, etc. • Aortic aneurysm screening • Focussed Assesment with Sonography for Trauma (FAST) scan for rapid diagnosis in trauma • Doppler US for assessing blood flow: -Evaluates movements by measuring changes in frequency of the echoes reflected from moving structures. -Adds information around physiology that other modalities cannot provide, e.g., foetal monitoring -Real time viewing of blood flow.
MRI
Strengths:
• Non-ionising and multiplanar
• Exquisite soft tissue contrast
Weaknesses:
• Limited availability to some referrers
• Very strong magnetic field
• Some patients/each %not suitable
• Expensive shielding
• Cannot see calcification or gas
Basics:
• Patient lies in scanner
• Hydrogen protons align to longitudinal axis of magnet
• RF pulse applied which causes protons to flip
• Recovery rate of these protons depends on the tissue they are in
• Resultant image has range of contrast.
Contraindications in MRI
- Cardiac pacemaker
- Implanted cardiac defibrillator
- Aneurysm clips
- Neurostimulator
- Insulin or infusion pump
- Implanted drug infusion device
- Bone growth/fusion stimulator
- Cochlear, otologic or ear implant
- Metal fragments in the eye
- NOT orthopaedic hardware.
Nuclear medicine
• Uses small amounts of radioactive substances to asses organ function, diagnose and treat disease.
• Radioactive tracers are usually administered via intravenous injection
• Radiation emitted is detected by gamma camera
Strengths
• Functional information
Weaknesses:
• Very limited anatomical information
• Radiation-patient/staff/population
Position emission tomography (PET)
- Patient injected with a positron emitting radiopharmaceutical such as fluorodeoxyglucose (FDG) Time allowed for drug to circulate the system
- PET scan detects patterns of distribution around the body.
- FDG is metabolised to FDG-6-phosphate which cannot be further metabolised by tumours cells
- It accumulates and concentrates in tumour cells. This accumulation is detected and quantified.
- Images are noisy and therefore usually combined with CT/MRI.
Hybrid imaging
- Fusion of 2 or more imaging modalities
- Gives information on anatomy and function
- Includes PET-CT & PET-MRI
- CT or MRI undertaken first
- Allow monitoring of disease progression
- Limited availability of scanners compared to CT & MRI.
Contrast agents in imaging
- Used in most modalities to improve the visualisation of organs, blood vessels and pathology
- May be injected, swallowed or administered rectally.
- Are eliminated from the body via urine, rectally or are absorbed.
Iodinated Contrast Media: • Pharmacological agents bound to iodine. • Radio-opaque • Non-iconic water-soluble compounds • Most contrast is 270-320mg l/ml Used in: • CT scanning • Angiography/interventional procedures
Risks with contrast agents
• Allergenic reactions- question patient history
• Avoid if possible in pregnancy- crosses to foetus
• Alternative contrast may be suitable (radiology decision
• Contrast induced nephrotoxicity- patient’s renal function must be established pre examination
• Poor renal function- exam undertaken based on risk/benefit assessment.
• Nephrogenic Systemic Fibrosis (NSF)
-Related to Gd contrast
-Affects skin mainly but can also affect lungs, heart, muscles
-Skin develops firm patched with oedema
-Develops over weeks
-Patients most at risk are those with severe renal disease.
3 conventional planes in image orientation
Axial (transverse), Coronal (frontal), Sagittal (lateral)
Interventional Radiology
- Image guided diagnostic or therapeutic procedure achieved through percutaneous puncture of a vessel or organ or via a body opening.
- Range of procedures from stent insertion, percutaneous abscess drainage to endovascular repair of aortic aneurysms.
Metallic stents
- Balloon expendable
- Self-expanding
- Allows resumption of blood flow artery
Drain insertions
Techniques include placement of/or reinsertion of nasogastric feeding tube or insertion of tubes for venous access (long term treatments).
How do we take a chest X-Ray
- Best result is achieved in X-Ray department
- Patient stands with chest to X Ray receptor
- Avoids magnification of heart
- Allows good inspiration
- Reduces dose to others
Anatomical terminology
Dorsal-Up Rostral- Front Ventral- Down Caudal- Back Medial- towards the centre Lateral- away from the centre
