Support and Protection by the Skeletal and Muscular System

• • Concept 1: Animals employ diverse strategies for support, protection, movement, and locomotion.
  • Concept 2: The skeletal system of humans serves a variety of functions.
  • Concept 3: The human skeletal system is composed

  of bones, cartilage, and joints.

  • Concept 4: Muscular system consists of all types of muscles.
  • Concept 5: Skeletal muscles, which helps in bone movement, are

  made up of smaller units.

  • Concept 6: The sliding filament theory of muscle contraction

  postulates that thin and thick filaments ratchet past

  each other powered by myosin molecules.
• Concept 1: Animals employ diverse strategies for support,

  protection, movement, and locomotion.


  • Skeletal & muscular systems – carry out support,

  protection, and locomotion in most animals

  > Some animals like sponges are incapable of movement
• Concept 1: Animals employ diverse strategies for support,

  protection, movement, and locomotion.

  • Three major types of skeletal system/skeleton among animals

  1. Hydrostatic skeleton
  2. Exoskeleton
  3. Endoskeleton
• • Three major types of skeletal system/skeleton among animals

  Hydrostatic skeleton

  > Made up of fluid held under pressure in a closed body compartment

  > Form and movement controlled by using muscles to change shape of

  fluid-filled compartments

  > Common among cnidarians, flatworms, annelids, nematodes
• • Three major types of skeletal system/skeleton among animals

  Exoskeleton

  • Hard covering on an animal’s surface
  • Shells of clams & some mollusks are made up of calcium carbonate, excreted by the mantle (sheet-like extension of body cavity)
  • Cuticle – jointed skeleton in arthropods; coat secreted by epidermis

  > Molting – shedding of exoskeleton when an arthropod grows
• • Three major types of skeletal system/skeleton among animals


  Endoskeleton

  • Hardened internal skeleton buried within soft tissues/cells
  • Spicules – endoskeleton of some sponges

  > Hard needle-like structures made of calcium carbonate/silica

  > Spongin protein – component of more flexible endoskeleton in some sponges

  • Ossicles – hard plates of magnesium carbonate & calcium carbonate crystals

  > Make up endoskeleton of echinoderms

  • Bone and/cartilage – make up endoskeleton of vertebrates
• Concept 2: The skeletal system of humans serves a variety of functions.

  Functions:

  • Framework of body supporting & protecting different organs

  > Bone & cartilage enclose and protect some vital organs (i.e., heart & lungs)

  • Bones act as levers for muscle attachment --> generates

  movement

  • Hemopoiesis – production of blood cells in red bone marrow in a segment of long bones
  • Store Ca & K+ and small amount of Mg+ and Na+
• Concept 3: The human skeletal system is composed of bones, cartilage, and joints.

  • Cartilage – connective tissue made up of collagen & chondroitin sulfate --> makes tissue strong yet flexible

  > Framework of vertebrate embryos --> replaced by bone during

  development
• Concept 3:

  The human skeletal system is composed

  of bones, cartilage, and joints.

  Bone – mineralized connective tissue; forms majority of

  skeleton

  • Osteoblasts – bone-forming cells which deposit collagen

  > Mature into osteocytes (maintain bone nutrition)

  • Osteoclasts – resorb/destroy bone and remodel damaged bones

  > Aid in Ca regulation in body

  • Osteons – repeating units of a hard bone

  > Has concentric layers of mineralized matrix deposited around central canal (with blood vessels and nerve cells)

  
• 5 major types of bones according to shapes:

  Short

  
• 5 major types of bones according to shapes:

  Long:

  • 2 main tissue membranes

  > Periosteum – outer connective tissue

  > Endosteum – inner connective tissue

  • 2 major segments

  > epiphysis

  > inner diaphysis

  
• 5 major types of bones according to shapes:

  Flat

  
• 5 major types of bones according to shapes:

  Irregular

  
• 5 major types of bones according to shapes:

  Sesamoid

  
• 2 Major Segments of the Bone

  • 2 epiphysis

  > Bone is spongy; soft & porous

  > Spongy bone contains red bone marrow (production of blood cells)

  > Cartilage surround epiphyseal ends of long bone

  • Inner diaphysis

  > Bone is compact; hard and solid

  > Compact bone contains yellow bone marrow (stores fats)

  A) Diaphysis

  B) Epiphysis

  C) Epiphysis

  
• Concept 3: The human skeletal system is composed of bones,

  cartilage, and joints.

  Ossification – process converting cartilage into a bone

  • Cartilage sores calcium and hardens into bone
  • Primary ossification – happens after birth

  > Bone hardening due to active intake & storage of Ca in bones

  • Secondary ossification – increases bone length

  > Happens in epiphysis or at epiphyseal line/disk/growth plate

  
• Concept 3: The human skeletal system is composed of bones, cartilage, and joints.


  3. 214 bones in children and 206 bones in adult

  • Difference due to fusion of bones in spinal column
  • 2 main divisions of human skeleton

  > Axial skeleton – all bones along body’s long axis

  > Appendicular skeleton – upper & lower extremities, pelvic girdle, shoulder girdle

  • Bones in the head

  > Cranial/skull (frontal, occipital, parietal, temporal bones)

  > Facial (mandible, maxillary)

  > Ear (malleus/hammer, incus/anvil, stapes/stirrups)

  > Hyoid bone

  A) axial

  B) appendicular

  
• Concept 3: The human skeletal system is composed of bones, cartilage, and joints.


  3. 214 bones in children and 206 bones

  in adult

  • In the trunk

  > 26 bones in spine/vertebral column

  • Appendicular skeleton

  > Bones in upper extremities (humerus, ulna, radius, carpals, metacarpals, digits)

  > Shoulder girdle (clavicle, scapula)

  > Pelvic girdle (pubis, ischium, ilium)

  > Lower extremities (femur, patella, tibia, fibula, tarsals, metatarsals,

  phalanges)
• Concept 3: The human skeletal system is composed of bones, cartilages, and joints.

  4. Joints – where bones are connected by

  ligaments

  • 3 major types of joints

  > Fibrous joints – joined by connective tissue

  > Cartilaginous – joined by cartilage

  > Synovial joints – contains fluid; freely movable

  
• Concept 4: Muscular system consists of all types of muscles.

  3 major types of muscle

  • Skeletal muscle
  • Smooth
  • Cardiac

  
• Concept 4: Muscular system consists of all types of muscles.


  Functions

  • Movement and locomotion

  > Bones serve as levers for movement

  > Force is generated by muscular system

  • Maintenance of body posture

  > Muscle tone – partially contracted state of muscle

  > Good muscle tone --> good body posture --> hallmark of good health

  • Thermoregulation

  > Shivering – muscle contractions associated with heat

  production

  > Bring back body temperature into normal when < 35.60C
• Concept 5: Skeletal muscles, which helps in bone movement, are made up of smaller units.

  Structure

  • Skeletal muscle --> muscle fascicles --> muscle fibers --> multinucleated cell --> myofibrils (made of thin and thick filaments) --> sarcomeres (basic contractile unit of skeletal muscles)

  > Thick filaments (myosin) – anchored to M line

  > Thin filaments (actin) – attached to Z line

  
• Concept 6: The sliding filament theory of muscle contraction postulates that thin and thick filaments ratchet past each other powered by myosin molecules.

  Steps in sliding filament theory

  
• Steps in sliding filament theory

  1. ATP still attached to myosin head keeping myosin in low-energy configuration

  2. Myosin head breaks down ATP into ADP & P thru hydrolysis turning myosin into its high energy configuration

  3. Myosin head will bind to specific sites in actin, forming a cross-bridge

  4. ADP & P will be released --> Myosin will return to its low energy configuration --> filament slides

  5. Myosin head will be released from actin when a new molecule attaches to myosin head --> new cycle