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Functional Anatomy and Embryology
Foundations of Biomedical Science 1
King's College London
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Functional Anatomy and Embryology
Lecture 1: Anatomical Terminology –
Anatomical Position: 1. Toes pointing forward 2. Eyes directed to the horizon 3. Arms by side 4. Palms of hands face forwards
Sagittal/Medial: vertical plane dividing body into left and right. Coronal/mid-axillary: Vertical plane dividing body into front and back Transverse/axial: horizontal plane dividing body into upper and lower parts. Mid-clavicular/parasagittal: divides body through clavicle (collarbone)
Term Meaning Anterior Towards front of the body Posterior Towards back of the body Superior Towards the head Inferior Towards the soles of the feet Medial Towards median plane Lateral Away from medial plane Proximal Towards the trunk Distal Away from the trunk Term Meaning Superficial Towards the skin surface Deep Toward interior of the body Internal Within a cavity External Outside a body cavity Ipsilateral On the same side Contralateral On the opposite side Name Shape Fibula Pin Cuneiform Wedge shaped Navicular Boat shaped Digastric Two bellies
proximal
Midclavicular
distal
Movements: Gliding – where two surfaces slide past each other, travelling a small distance (midfoot) Flexion – decreases angle at joint Extension – increases angle at joint Abduction – move away from the mid-line Adduction – towards the mid – line External (lateral) – turn away from the mid-line Internal (medial) – turn towards the mid-line
Movement Action Pronation Turn palmar surface of hand to face posteriorly Supination Turn palmar surface of hand to face anteriorly Inversion Turn plantar surface of foot medially Eversion Turn plantar surface of foot laterally
Lecture 2: Building Tissues from Cells –
Epithelia are sheets which cover the body surface (epidermis) Line almost all internal cavities + rest on basement membrane Depend on diffusion for nutrients – blood vessels (always below) never pass through basement membrane Base ment membrane = extracellular matrix (proteins outside of cell). Dense meshwork.
Classifying Epithelial Tissues: 1. Cell Shape:
Function of Cell Junctions: 1. Keeps epithelial sheets tightly bound – anchoring junctions 2. Allows functional integrity of cells – selective barriers or communication
Junctions:
Anchoring: done by Desmosomes and Hemidesmosomes
Intermediate filaments = rope like to facilitate bending in epithelial sheets.
Adherens Junction – linked by bundles of actin filaments:
Non-Anchoring Junctions: 1. Tight – barrier junction 2. Gap – selective communication between cells
Name Function Tight Junction Seals neighbouring cells together in epithelial sheet to prevent leaking of molecules between them Adherens Joins actin bundle in one cell to similar bundle in neighbouring cell Desmosome Joins intermediate filaments in one cell to those in neighbour Gap Junction Allows passage of small water-soluble ions and molecules Hemidesmosome Anchors intermediate filaments in a cell to basal lamina (basement membrane)
Tight Junctions: Brings individual membranes of two cells so close together so nothing can move between cells Useful e. in upper part of small intestine where molecules are absorbed. High nutrient concentrations above cells which are moved away by blood capillaries but water from below would attempt to dilute this – tight junction used. Sometimes RARELY seals can be relaxed so let very small molecules through Made of homophilic binding of claudin and occludin
Gap Junctions: Allows exchange of small molecules between cytoplasms of neighbouring cell. Allows molecules to equilibrate.
Lecture 3: Tissue Organisation – Cellular Basis –
Soft Connective Tissue: Consists of cells embedded in ECM. Cells synthesise and secrete Extra-cellular matrix (ECM). Can be deformed slightly and reform. ECM is of variable composition & depends on function of ECM **Fibroblast produces ECM
Functions of soft connective tissue: 1. Space filler – separate 2 layers of tissue 2. Provide mechanical support – strength 3. Allows attachment of other cell layers + cell within it 4. Protection (dermis of skin) 5. Highway for nutrients 6. Storage of fat (adipose tissue) and calcium (bone + calcium repository) 7. Site of immunological defence
Types of Soft Connective Tissue and Location: Type Location Mesenchyme Embryonic (looks unspecialised) Loose (areolar) Mesentry, under dermis inc. hyperdermis Dense Tendon (muscle to bone), dermis, capsules around muscles Reticular (look like stars). Bone marrow, lymph nodes Adipose Fat cells. Hyperdermis of skin, around major body organs
Adhesive Proteins: Bind to transmembrane receptors integrins Attach cells to matrix Types: 1. Fibronectin – abundant in all CT 2. Tenascin – produced at wounds – not 100% on function 3. Laminin – i n basal lamina, binds epithelia to basal lamina.
GAGs: GAGs are attached to a core protein to form proteoglycans EXCEPT hyaluron (GAG) All GAGs have similar structure: amino group on hexose sugar and carboxyl group on other one. Repeating subunits from 70 -200 sugars long Very high density of negative charge Very hydrophilic – absorbent. Water sucked into matrix by osmotically active ion cloud. Water creates swelling pressure (turgor) that enables ECM to withstand compressive forces.
Cells of connective tissue: 1. Indigenous: synthesis of ECM, lipid storage 2. Immigrant: immune system cells
Indigenous cells: All stem from mesenchymal stem cells APART FROM MAST CELLS - Fibroblasts: ECM producer - Adipocytes: fat storage, leptin secretion (regulates appetite) - MAST CELLS: actually formed in embryo but migrate into connective tissues. Histamine production and immune response. Immigrant Cells: Largely leukocytes – WBC: - Neutrophils, monocytes/macrophages – phagocytic - Dendritic cells – immune surveillance - Eosinophils – parasitic infection - Basophils – obscure function - Lymphocytes – antibody production, cell killing
Lecture 4: Tissue Organisation – Topographical Basis –
Somatic: body as whole. Describes elements which make up walls of trunk and limbs inc. bone, cartilage + skeletal muscle. Supplied by somatic nervous system Visceral: bowels + organs in trunk and head and neck (heart, liver). Organs supplied by autonomic nervous system (visceral).
Skin: covers outer surface of body Functions: 1. Protection (waterproof) 2. Thermoregulation 3. Sensory info about surrounding environment 4. Vit D synthesis. Consists of 3 layers: 1. Epidermis 2. Dermis 3. Superficial fascia (hypodermis)
The Epidermis: composed of keratinocytes (90%) + 3 less abundant cell types – melanocytes, Langerhans cells and Merkel cells Dermis: comprised mostly of connective tissue with collagen and elastic fibres, fibroblasts, macrophages and adipocytes. Superficial Fascia: found immediately below dermis and contains collagen and elastic fibres BUT ASLO varying amounts of fat except in ear and eyelid.
Functions of Superficial Fascia: 1. Storage of water and fat 2. Protection against mechanical shock as fat and water act as cushion 3. Thermal insulation as fat & water provide effective barrier against rapid heat loss 4. Conduction transport nerves and blood vessels to skin
Deep Fascia: beneath superficial. Highly organised connective tissue layer (has ECM). Allows compartmentalisation. Unlike superficial fascia, deep fascia has little fat and collagen fibres are more organised.
Functions of deep fascia: 1. Conduction – blood vessels and nerves wrapped in deep fascia neurovascular bundles which travel around the body 2. Movement of muscle – muscles wrapped in deep fascia can slide over each other 3. Attachment for some muscles – some muscles gain partial attachment from deep fascia 4. Capsules around organs and glands
Serous Membranes: three serous membranes line internal cavities of body consisting of mesothelium and supported by loose connective tissue – 1. The Pleura – lungs 2. The Pericardium - heart 3. The Peritoneum – around contents of abdomen All membranes are thin double layered structures w/ inner layer attached to viscera and outer layer anchored to body wall. Small space between 2 layers filled with fluid to minimise friction.
Cartilage: Firm, flexible connective tissue Consists of chondroblasts (secrete ground substance and collagen to form a rigid gel) Once formed, cells remain in situ as chondrocytes No neurovascular (nerves/blood vessel) in cartilage. Gains nutrients by diffusion through ground substance cartilage is thin Foetal skeleton preformed in hyaline cartilage (present in joints, respiratory tract + immature skeleton) + remains in adult as articular surface on joints + regions of elasticity
Hemopoiesis: stem cells which give rise to other blood cells. Process occurs in red bone marrow (flat bones + spongy material at end of long bones of femur and humerus)
Calcium in blood must be kept constant but we eat intermittently so must be stored until required. Controlled by parathyroid hormone.
Intramembranous Ossification – forms flat bones of skull, face, jaw + centre of clavicle. Formed in sheet like layers resembling a membrane Endochondral Ossification – forms most bones in body, mostly long bones, replace cartilage with bone
Structure of Mature Bone: Consists of compact bone and trabecular (spongy) bone Compact bone appears solid vs trabecular bones appear as open network of struts Compact bone structure allows stress resistance from limited directions Trabecular bone more capable of stress resistance from multiple directions so found in epiphysis of long bones.
Joints: union between 2 bones 1. Fibrous – united by collagen 2. Cartilaginous – united by cartilage 3. Synovial – fluid filled cavity separates skeletal elements which are united by fibrous capsule
Fibrous Joints: 1. Sutures – fond only between skull bones 2. Syndesmoses – interosseous membranes (broad and thin plane of fibrous tissue that separates many of the bones of the body). 2 bony components slightly apart, connected by interosseous membrane. Little movement allowed (radius and ulna) 3. Gomphoses: found only between bones and teeth. Has form of peg in a socket root of tooth in jaw.
Sutures: In foetal skull, sutures are wide, and bones present smooth opposing surfaces. Allows slight degree of movement between skull bones during passage of head through birth canal. After birth, sutures become rigid, allowing no movement They develop into one of three types: - Squamous - Serrated - Denticulate
Cartilaginous Joints: 1. Primary: Synchondroses – develop between bones of endochondral origin. Solid plate of hyaline cartilage between opposing surfaces. Cartilage plate provides area for growth. 2. Secondary: Symphyses – partially moveable joint in which opposing surfaces covered by hyaline cartilage but separated by fibrous tissue. Found in midline of body.
Synovial Joint Components: 1. Articular cartilage: Ends of bones are covered in hyaline cartilage which is tough but deformable. 2. Joint cavity – Ends of bone separated by cavity which contains 5ml of synovial fluid 3. Joint capsule – Surrounds joint like sleeve. Consists of bundles of collagen fibres and may vary in thickness. Thickenings of capsule called ligaments. 4. Synovial membrane – capsule lined by synovial membrane (but not articular surfaces) + has rich capillary network. Capable of secretion and absorption of fluid. Viscosity of fluid changes with speed of joint movement, becoming thinner as speed increases. 5. (Disc) – May be inserted between articular surfaces, dividing joint into 2 cavities + increasing range of possible motion. 6. (Bursae Sacs) – filled with synovial fluid. Most are found near to the joint. Occur in places where structures which are very close to each other.
Movements at Synovial Joints depend on: 1. Shape of articulation (joint) 2. Tension of joint capsule 3. Position of ligaments 4. Position of muscles surrounding joint
- Isometric – muscle exerting force without changing length e. pulling against immovable object postural muscles
Key Terms: Term Description Prime mover Agonist muscles Antagonist Opposes action of prime mover Fixator Steadies/holds position through isometric contraction Synergist Complements action of prime mover, either with same movement or by acting as fixator of intervening joint
Structure + Connective Tissue of Skeletal Muscle: Three separate layers of connective tissue that hold muscle fibres in position – 1. Epimysium – tough outermost layer that surrounds entire muscle (epi = upon) 2. Perimysium – surrounds bundles of muscle fibres to create fascicle (peri = around) 3. Endomysium – surrounds each muscle fibre within the fasciculus (endo = within)
Formation of Skeletal Muscle: Myoblasts fuse into myotubules (immature muscle fibres) – 1. Single cell – myoblast 2. Proliferation – encouraged to divide by being placed in growth factor medium 3. Fusion – low growth factor concentration makes them differentiate and form myotube Myogenic Regulatory Factors (MRFs) are transcription factors which cause differentiation
Satellite Cells: Muscle fibres are specialised post-mitotic cells On muscle fibre surface are population of stem cells satellite cells Can be activated to enter cell cycle and become myoblasts They self-renew to maintain stem cell population Important for: 1. Muscle growth after birth 2. Muscle repair and regeneration 3. Muscle hypertrophy (bigger) 4. Muscle maintenance
Sarcomere – Contractile Unit: Striations – alternating light and dark bands across length of fibre - Thick filaments: myosin dark stripes (A band) - Thin filaments: actin light region (I band) Myofibrils divided into sarcomeres Myofibre filled with many myofibrils In centre of sarcomere portion of myosin filament with no overlap of actin = H zone Sarcomeres separated by Z-lines
Sliding Filament Model – Muscle Contraction: 1. Sarcomere shortens (Z lines move closer) 2. I band and H zone shortens 3. A band remains same length
Subdivision of Muscle Fibres: Subdivided according to speed of contraction Basic division into Type I slow and Type II fast - Fast myosin isoform (grey) found in white muscle fibres (small amount of myoglobin – oxygen binding protein) - Slow myosin isoform (pink) found in red muscle fibres (lots of myoglobin) Fast fibres divided: IIa, IIb, IIx Most muscles have varying proportions of different fibre types
Muscle Innervation: Myofibre receives innervation from 1 motor neurone Motor end plate/NMJ: specialised area on muscle fibre membrane where nerve contacts Each motor neurone contacts multiple muscle fibres – motor unit Motor unit size dictates degree of muscle control – small in hand and eye, larger in leg
Set of muscle fibres innervated by axonal branches of single motor neuron of CNS motor unit
Dystrophin: Is a gene on X chromosome Dystrophin helps link contractile apparatus to ECM and helps stabilise sarcolemma during contraction In muscular dystrophy – muscle tears itself apart (lack of dystrophin) - Healthy muscle contractile units can be replaced by adipose tissue OR re generation of damaged tissue causes necrosis.
Effects of Ageing and Exercise on Muscle Tissue: Mature muscles can grow hypertrophy (individual muscle cells get bigger after exercise) With age, ability to repair/build new muscle diminishes Muscle is also replaced by adipose or fibrous tissue that can impede function further
Muscle Formation: All trunk and limb muscles are derived from embryonic structures called somites. Repeating blocks of tissue.
Not all skeletal muscles have same embryological origin
Muscle precursors must migrate into limb bud to form limb muscles.
Supporting Cells of PNS: 1. In PNS cell bodies are found in ganglia and supported by satellite cells 2. Axons supported by Schwann cells which either myelinate a section up to 1mm in length 3. OR form a simpler relationship where several axons are enclosed in the Schwann cell
Ganglia: Nerve cell bodies of neurones which lie outside CNS & collected into groups called ganglion Supported by satellite cells Sensory ganglia – no synapse and neurons termed pseudo unipolar Motor ganglia – synapses and neurons are multipolar
Major Divisions of Brain: Supporting/Protecting Brain + Spinal cord: Brain and spinal cord surrounded by bone which forms rigid barrier Where nerves enter and leave the brain & spinal cord foramina in skull + vertebral column to allow connection with other body regions. Meninges support brain and contains cerebral spinal fluid to allow brain to float and absorb shock
Layers of Meninges: 1. Dura Mater – 2 layered structure w/ outer layer fusing w/ periosteum and lining cranial cavity. Inner layer has several specialised folds which further support brain. Venous sinuses run in gaps between 2 layers 2. Arachnoid Mater – covers brain surface and ͞deep͟ to it lies suďaraĐhŶoid spaĐe which contains meshwork of collagen and elastic fibres linking it to Pia Mater. Cerebrospinal fluid fills this space 3. Pia Mater – tightly attached to brain by astrocytes and follows its contours.
Peripheral Nervous System: Cell bodies in PNS organised into ganglia. Axons leave CNS to supply motor fibres to muscles (skeletal + sensory) and collect sensory info. Axons in PNS collected in bundles called nerves 1. Somatic nerves – supply body wall, skeletal muscle, skin (contain both motor + sensory fibres) 2. Nerves of Special Sensation – sight, smell, taste, hearing & balance. 3. Autonomic Nerves – supply internal organs with motor (smooth muscle) and sensory fibres
Spinal Nerves = somatic nerves and those of special senses, if they originate from spinal cord
Lecture 8: Organisation of the Nervous System II –
ANS – involved in regulating internal environment of body. They have both motor and sensory components Sensory fibres – travel mostly with motor fibres and have cell bodies in posterior root ganglia. Motor Fibres – innervate smooth muscles and glands but in GIT modulate activity of ANS.
ANS has 2 major divisions: 1. Sympathetic 2. Parasympathetic Many organs receive fibres from both divisions which are usually antagonistic to each other. Sympathetic speeds up heart, parasympathetic slows down
Sympathetic: 1. Arises – T1 to L 2. Distribution – all parts of body wall and viscera 3. Function – moderate visceral functions e. heart rate, peristalsis, sweating 4. Strong sympathetic response: - Staring eyes - Cold, clammy skin - Dry mouth
Parasympathetic: 1. Arises – Cranio-sacral. o Cranial nerves III, IV, IX, X (vagus nerve) o Sacral spinal nerve S2-S 2. Distribution- Head and trunk only 3. Function – regulating normal function of organs it supplies
Cranial Nerve X (Vagus): Has post ganglionic neurons in wall of structure its going to innervate (intramural ganglia). Target organs: - Visceral organs of neck, head, thoracic cavity + most of abdominal cavity
- Surface rendering
- Volume rendering
Historical Timeline: 1. Proof of concept (but no practical implementation) - Supported by mathematical or physical arguments 2. Practical implementation in phantoms or animals 3. Practical implementation in clinical patients Projective X-rays used from 1985 onwards (most widely used form of imaging) Removal of needle from hand 1986 X-ray contrast agents from 1906
X-ray Generation: Produced when high speed electrons strike a target material (Tungsten) Maximum energy of x-rays depends on speed of electrons X-ray measured in keV (typically 30-100 keV)
Laŵďert Beer͛s Laǁ: X-rays follow negative exponential curve
I 0 = X-rays coming with intensity of I 0 X = path length of object X-ray needs to pass through u = Linear attenuation coefficient (property for each material)
Radiographic Contrast: Arises due to differences in u and x
Detection of X-rays: Screen-film combinations Image intensifiers Flat panel detectors
Foundations for Computed Tomography (CT): Problem with projective X-rays is that all structures are superimposed so the depth of the objects are not known. 1961 first CT image 1972 first practical realisation of CT
Trends in CT: Faster scanning – more images per second Lower radiation dose – less mSv (radiation dose – millisievert) Interventional – real-time imaging Spectral – can resolve X-ray images Multisource – more than 1 tube
Lecture 10: Imaging Technologies II –
Alpha decay: Unstable radionucleotide ejects alpha particle (helium nucleus: He2+) Equation: AZX A-4Z-2Y + 42 He
Beta-Minus Decay: Neutron proton + beta(-) + antineutrino
Beta-Positive Decay: Proton neutron + beta(+) + neutrino
Positron Annihilation and Detection: Tracer decays and emits positron Annihilation occurs with electron 2 gamma photons emitted in complete opposites to each other (photons strike opposing detectors)
Decay Kinetics: Decay rate dN/dt = - ɶ N dN/dt = radioactivity ɶ = decay constant N = number of nuclei
Radioactive Decay: Penetrating ability:
Half Life: time taken for half the nuclei to decay calculated by: lŶ;ϮͿ / ɶ
Type of scan Characteristics Images Position Emission Tomography (PET) 1953
Uses radioactive tracers to measure blood flow, O use etc.
Functional Anatomy and Embryology
Module: Foundations of Biomedical Science 1
University: King's College London
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