Basic Anatomy and Physiology

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Basic Anatomy and Physiology

• The objective of these lectures is to describe
  some important structures of the human body to
  set the stage for where Biomechanical Engineers
  work.

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Anatomical Directions (or Axes)

• Directions (Absolute)
• anterior/posterior
• superior/inferior
• medial/lateral
• Directions (Relative)
• proximal/distal

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Anatomical Planes

• Planes
• Frontal or Coronal
• Saggital
• Transverse

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Musculoskeletal System

• The musculoskeletal system is the organ system
  that gives animals the ability to move
  (locomotion). The primary functions of this
  system include
• Providing Physical Form and Stability
• Allowing Motion
• Providing Protection
• The musculoskeletal system is comprised up of the
  following tissues
• Muscles
• Bones
• Cartilage, Ligaments, Tendons
• Joints

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Muscles

• Muscle tissue consists of specialized cells that
  can shorten in response to electrical
  stimulation.
• Three types of muscle tissues
• Cardiac (heart)
• Smooth (walls of blood vessels, orifices)
• Skeletal (attached to bones via tendons)

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Skeletal Muscles
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Muscle Cells (or Fibres)
Each skeletal muscle cell (or fibre) fiber has
many bundles of myofilaments and each bundle is
called a myofibril. The myofilaments of a
myofibril are arranged in a regular fashion so
that their ends are all lined up. This is what
gives the muscle its striated appearance.
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Sarcomeres
The contractile units of muscle cells are called
sarcomeres (up to 10,000 sarcomeres can be
contained in each cell) which shorten in response
to calcium ions.
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Motor Unit
A motor unit is a single motor neuron and all of
the corresponding muscle fibers it innervates.
When a motor unit is activated, all of its fibers
contract. Groups of motor units often work
together to coordinate the contractions of a
single muscle.
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Bones

• Bones are specialized connective tissues
  (mineralized) and make up 18 of body mass.
• Two types of bones
• Spongy (cancellous or trabecular)
• Ends of long bones, interiors of others
• Porous and made of tiny struts (trabeculae)
• Compact (cortical)
• Forms the shaft and outer covering of almost all
  bones
• Dense structure made up of stacked layers
  (lamellae)

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Cortical and Cancellous Bone
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Cortical and Cancellous Bone
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Bone Remodeling

• Bone is a living tissue and is constantly
  remodeled by two different types of cells
• Osteoclasts (bone-resorbing cells)
• Osteoblasts (bone-forming cells)
• Bone remodeling occurs
• During growth
• To repair accumulated micro-damage

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Bone Remodeling

• Average skeleton is totally remodeled every 10-20
  years.
• Imbalance in the remodeling cycle (resorption vs.
  deposition) normally happens with age and a large
  imbalance results in a disorder called
  osteoporosis (weak, brittle bones).
• Osteoporotic bones are more susceptible to
  fracture.

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Fracture

• Bone can normally heal itself after a fracture
  but in extreme cases interventions are required
  (fracture fixation plates and screws).

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Cartilage, Ligaments and Tendons

• Cartilage, ligaments and tendons are all
  connective tissues primary comprised of fibrous,
  load bearing proteins (collagen and elastin)
  embedded in a polysaccharide gel
  (proteoglycan-water matrix).

The tissue structure resembles a fibre-reinforced
composite material.
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Cartilage

• Articular Cartilage is the resilient tissue that
  lines of articulating bones and forms the natural
  bearing surfaces of joints.

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Ligaments

• Ligaments are cable-like fibrous tissues that
  connect bone-to-bone to provide joint stability.

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Tendons

• Tendons are calble-like fibrous tissues that
  connect muscle-to-bone, functioning simply to
  transmit forces

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Connective Tissue and Joints
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Joints

• Bones are connected to one another by different
  types of joints
• Fibrous
• Bound tightly together by fibrous connective
  tissue
• Suture joints of the skull
• Cartilaginous
• Bound together by a layer of cartilage
• Vertebral column (disc between vertebrae) and
  attachments of ribs to the sternum
• Synovial
• Most complex joints
• Allow a large degree of relative motion between
  articulating bones
• Articulating bones lined with a lined with a
  layer of cartilage and separated by a thin layer
  of lubricating fluid (synovial fluid)
• Surrounded by a fibrous capsule (synovial
  capsule)
• Hip, knee, elbow, ankle, etc.

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Synovial Joints

• Six different types of synovial joints, each of
  which are classified by the type(s) of motion
  they permit
• Pivot(1 DoF)
• Ball and Socket (3 DoF)
• Hinge (1 DoF)
• Ellipsoid (2-3 DoF)
• Saddle (2 DoF)
• Gliding (1 DoF)

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Total Joint Replacements

• Artificial joints have been developed to replace
  damaged (trauma) or diseased (osteoarthritis)
  joints in which the cartilage layer(s) that line
  the ends of the articulating bones has been
  destroyed.
• Resurfacing technique (metal and plastic) and
  almost all joints have available replacements
  with the most common being the hip and knee

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Cardiovascular System

• Cardiovascular system provides several functions
• delivery of nutrients, hormones and signaling
  molecules
• removal of metabolic waste products from tissues
• primary mechanism for temperature regulation
• These functions are carried out through the
  movement of blood and at the centre of this is
  the heart (pumping station that moves blood
  throughout the body)

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Anatomy of the Heart

• Four-chambered muscular vessel
• Two Atria (left and right)
• Two Ventricles (left and right)
• Atrium
• Filling chamber
• Pushes blood into ventricle
• Ventricle
• Pressurization chamber
• Ejects blood into circulation
• Chambers separated by heart valves
• One-way flow valves
• Four in total (tricuspid, pulmonary, mitral,
  aortic)

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Pulmonary and Systemic Circulations

• Essentially two separate pumps
• Right Side
• moves deoxygenated blood to the lungs for
  oxygenation
• Left Side
• moves oxygenated blood to the body
• Which leads to two distinct circulatory systems
• Pulmonary
• vessels to and from the lungs
• Systemic
• vessels to and from the rest of the body
• Vessels that move blood away from the heart are
  called arteries and vessels that return blood to
  the heart are called veins.

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Cardiac Cycle

• Blood returns to the heart from the circulation
  (pulmonary or systemic) and collects in the
  atrium.
• The atrium contracts and pushes the blood into
  the ventricle (the major pumping chamber).
• The ventricle then contracts, pressurizing the
  blood and the ejecting it into the circulation.

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Blood Vessels (Arteries and Veins)
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Atherosclerosis

• Atherosclerosis is a disease state where deposits
  of fatty substances, cholesterol and other
  substances build up in the inner lining of an
  artery (plaque), thereby restricting blood flow.

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Angioplasty and Stents

• Angioplasty is the technique of mechanically
  widening a narrowed or obstructed blood vessel.
  Tightly folded balloons are passed into the
  narrowed locations and then inflated to a fixed
  size using water pressures of 6 to 20
  atmospheres.
• This procedure can be combined with a stent, an
  expandable tubular scaffold, used to keep the
  vessel open after inflation of the balloon.

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Heart Valves

• Special one-way valves keep blood moving in the
  correct direction.
• The when atria contract, the atrioventricular
  valves (tricuspid and mitral) open to allow blood
  to pass into the ventricles.

When the ventricles contract the semilunar valves
(aortic and pulmonary) open to allow blood to
leave the heart, while at the same time the
atrioventriclar valves are closed to prevent
back-flow into the atria. When the ventricles
relax before the next contraction, the semilunar
valves close to prevent blood flowing back into
the heart.
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Heart Valve Disease and Replacements