Skeletomuscular System Notes

Animal Characteristics

  • Being an animal means belonging to Kingdom Animalia, characterized by:
    • Multicellularity
    • Sexual reproduction
    • Heterotrophic nutrition (obtaining nutrients from external sources)
    • Motility - the ability to move
    • Muscles, nerves, and skeletons working in coordination for movement.

Vertebrates

  • Vertebrates belong to the Phylum Chordata.
  • Includes fish, amphibians, birds, mammals, and reptiles.
  • Tiktaalik:
    • An ancient vertebrate (375 million years ago).
    • Represents the transition from sea to land.

Tiktaalik Video

  • The video likely discusses the transition from fish to tetrapods (four-legged vertebrates).
  • Considerations when watching:
    • What specific features indicate this transition?
    • How did researchers determine where to search for fossils?
    • What geological aspects were they looking for?
    • What was the environment like in Pennsylvania 365 million years ago?
    • What are strata?
    • What specific features were being sought in the fossil?
    • Where was the Tiktaalik fossil eventually discovered?
    • What fish-like and tetrapod-like features did Tiktaalik possess?

Skeletal System

  • Functions of the skeletal system:
    • Support for the body.
    • Protection of internal organs.
    • Connection points for muscles, enabling movement.
    • Mineral storage, especially calcium.
    • Production of red blood cells.

Skeletal System Parts

  • Cartilage:
    • Protects the ends of long bones (e.g., femur).
    • Component of the ribcage structure.
  • Bones:
    • Typically 206-270 bones in the human body.

Bones and Ligaments

  • Ligaments:
    • Connect bones to each other.
  • Anterior Cruciate Ligament (ACL):
    • A common injury among athletes.
    • Function:
      • Prevents forward movement of the tibia.
      • Prevents hyperextension of the knee.

Divisions of the Skeletal System

  • Axial Skeleton:
    • Includes the skull, vertebrae (backbone), and ribs.
  • Appendicular Skeleton:
    • Includes the arms, legs, and hip bones.

Bone Structure

  • Bones are living tissue with an inorganic matrix.
  • Compact Bone:
    • The outer layer, very hard and dense.
  • Spongy Bone:
    • The inner layer, lighter but still strong.
  • Marrow:
    • Located within bones, responsible for red blood cell production.

Bones and Calcium

  • Calcium is a crucial nutrient for various bodily functions:
    • Blood clotting
    • Nerve impulse transmission
    • Enzyme activity
    • Muscle contraction

Bone Cells

  • Osteoblasts:
    • Bone cells that build bone by depositing calcium from the blood.
  • Osteoclasts:
    • Bone cells that break down bone using acids and enzymes, releasing calcium into the bloodstream.

Osteoporosis

  • Osteoporosis:
    • A condition where bone reabsorption (breakdown) exceeds bone deposition (building).
    • Results in weakened bones and increased fracture risk.
    • Common in post-menopausal women due to decreased estrogen levels.

Evolution of Skeletons

  • Various types of skeletons exist in the animal kingdom, not just in vertebrates:
    • Endoskeleton
    • Hydrostatic skeleton
    • Exoskeleton

Endoskeleton

  • Endoskeletons:
    • Hardened internal structures.
    • Composed of bone, cartilage, or silica.
    • Advantages:
      • Lighter weight.
      • Greater motility.
    • Disadvantage:
      • Less protection compared to exoskeletons.
    • Examples: Sponges (silica), bone, and cartilage.

Hydrostatic Skeleton

  • Hydrostatic skeletons:
    • Utilize pressure within the body cavity.
    • Muscles push against fluid to create movement.
    • Most animals with hydrostatic skeletons are aquatic.

Exoskeleton

  • Exoskeleton:
    • A hard, external covering with muscle attachments.
    • Provides significant protection.
    • Drawbacks:
      • Heavy.
      • Restricts growth – requires molting.
    • Examples: insects, crustaceans.

Muscular System

  • Functions in homeostasis in mammals:
    • Regulates body temperature.
    • Enables movement.
      • Voluntary: Consciously controlled movement.
      • Involuntary: Automatic, unconsciously controlled movement.

Skeletal Muscle

  • Skeletal Muscle:
    • Attached to bones via tendons.
    • Nervous system signals muscles to contract or relax.
    • Muscles can only contract and relax.
    • Contraction requires energy from ATP (adenosine triphosphate) molecules.

Paired Muscles

  • Muscles often work in pairs as agonists and antagonists.
    • Agonist muscles:
      • Produce a desired movement (e.g., biceps brachii).
    • Antagonist muscles:
      • Produce the opposite effect (e.g., triceps brachii).

Smooth Muscle

  • Smooth muscle:
    • Primarily responsible for internal movements.
    • Examples of functions:
      • Digestion
      • Uterine contractions during childbirth
    • Involuntary control.

Cardiac Muscle

  • Cardiac muscle:
    • Found in the heart.
    • Responsible for heartbeats.
    • Pumps blood, oxygen, and nutrients throughout the body.
    • Involuntary control.

Types of Muscle

  • Summary of muscle types (skeletal, smooth, and cardiac).

Group Activity

  • Create test questions to share with another group.
  • Question types: multiple choice, matching, short answer.