Support Systems and Locomotion

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Support Systems and Locomotion

• Chapter 41

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Outline

• Hydrostatic Skeleton
• Exoskeletons
• Endoskeletons
• Human Skeletal System
• Axial Skeleton
• Appendicular Skeleton
• Human Muscular System

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Hydrostatic Skeleton

• A fluid-filled gastrovascular cavity, or a
  fluid-filled coelom, can act as a hydrostatic
  skeleton.
• Offers support and resistance to the contraction
  of muscles for mobility.
• Annelids are segmented, and have septa that
  divide the coelom into compartments.

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Locomotion in an Earthworm
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Exoskeletons and Endoskeletons

• Exoskeleton - External Skeleton
• Molluscs (calcium carbonate) and Arthropods
  (chitin).
• Endoskeleton - Internal Skeleton
• Echinoderms and vertebrates.
• Bone and cartilage which grows with the animal.
• Does not limit space for internal organs, and
  supports greater weight.

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Vertebrate Endoskeleton
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Human Skeletal System

• Skeleton supports and protects the body while
  also permitting flexible movement.
• All bones store calcium and phosphate ions, and
  certain bones produce red blood cells.

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Bone Growth and Renewal

• Cartilage structures in early development act as
  models for future bones.
• Calcium salts deposited in matrix by cartilage
  cells and later by osteoblasts.
• Endochondral ossification
• In adults, osteoclasts break down bone, remove
  worn cells, and deposit calcium in the blood.
• Osteoclasts and osteoblasts work together to heal
  broken bones.

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Anatomy of a Long Bone

• Longitudinal section of a long bone shows a
  hollow cavity, medullary cavity, bounded at the
  sides by compact bone and at the end by spongy
  bone.
• Compact bone contains many osteons where
  osteocytes lie in lacunae.
• Spongy bone has numerous bars and plates
  separated by irregular spaces.
• Spaces filled with red bone marrow.

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The Axial Skeleton

• The axial skeleton lies in the midline of the
  body and consists of the skull, vertebral column,
  sternum, and ribs.

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The Skull

• Formed by cranium and facial bones.
• Bones of cranium contain sinuses.
• Major bones are named after the lobes of the
  brain and the facial bones.
• Foramen magnum is opening at base of skull for
  spinal cord to pass.

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The Skull
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Vertebral Column

• Vertebral column supports the head and trunk and
  protects the spinal cord and roots of spinal
  nerves.
• Cervical - Neck
• Thoracic - Thorax
• Lumbar - Small of back
• Sacral - Sacrum
• Coccyx - Tailbone
• Intervertebral disks of fibrocartilage act as
  padding.

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Rib Cage

• Thoracic vertebrae are part of the rib cage.
• Twelve pairs of ribs.
• Seven pairs of true ribs.
• Connect directly to sternum.
• Five pairs of false ribs.
• Do not connect directly to sternum.
• Rib cage protects the heart and lungs, and
  assists breathing.

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The Rib Cage
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The Appendicular Skeleton

• The appendicular skeleton consists of the bones
  within the pectoral and pelvic girdles and the
  attached limbs.
• Pectoral girdle - Arm and hand.
• Pelvic girdle - Leg and foot.

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Classification of Joints

• Fibrous Joints - Immovable.
• Between cranial bones.
• Cartilaginous Joints - Slightly Movable.
• Between vertebrae.
• Synovial Joints - Freely Movable.
• Bones separated by a cavity.
• Ligaments bind bones together.
• Knee

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Knee Joint
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Human Muscular System

• Skeletal muscles are attached to the skeleton by
  fibrous connective tissue, tendons.
• Can only pull, cannot push.
• Antagonistic pairs.
• A muscle at rest exhibits tone, dependent upon
  tetanic contractions.
• Maximal sustained contractions.

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Antagonistic Muscle Pairs
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Microscopic Anatomy and Physiology

• Sarcolemma
• Plasma membrane
• Sarcoplasmic Reticulum
• Modified endoplasmic reticulum.
• Myofibrils
• Contractile portions of muscle fiber.
• Sarcomeres
• Protein filaments within contractile units.
• Myosin
• Actin

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Sliding Filament Model

• Sliding Filament model states actin filaments
  slide past myosin filaments because myosin
  contain cross-bridges which pull the actin
  filaments inward.
• Working muscles require ATP.
• Myosin breaks down ATP.
• Sustained exercise requires cellular respiration
  for the generation of ATP.

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Muscle Innervation

• At a neuromuscular junction, nerve impulses bring
  about the release of a neurotransmitter that
  signals a muscle fiber to contract.

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Neuromuscular Junction
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Review

• Hydrostatic Skeleton
• Exoskeletons
• Endoskeletons
• Human Skeletal System
• Axial Skeleton
• Appendicular Skeleton
• Human Muscular System

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