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.
