Anatomy: Musculoskeletal System and Human Tissue

Anatomy of the Human Body: The Musculoskeletal System

Tissues of the Human Body

• The chemical level is the relationship between atoms that create molecules.
• An organelle is a collection of molecules forming a young intracellular body with a specific function within the cell.
• A cell is the basic structural and functional unit of the living body, containing numerous organelles.
• A tissue is a cluster of cells with similar structure and function.
• An organ comprises various tissues performing specific functions within a system, such as the heart, liver, or brain.
• A system consists of several organs working together to perform a specific function, like the respiratory or cardiovascular system.
• The complete body is the integration of all body systems, including the nervous, muscular, and skeletal systems.

Cellular Organelles

• The cell membrane is a selective barrier enclosing the cell.
• Mitochondria generate energy through respiration.
• The nucleus contains the DNA molecule, carrying the genetic information.
• The Golgi apparatus is responsible for protein production in the cell.
• Ribosomes are the site of protein synthesis, connecting amino acids.
• Lysosomes facilitate intracellular digestion and waste processing.

The Four Main Tissue Types in the Human Body:

• Epithelial tissue: Covers external and internal surfaces of the body, lining various organs and cavities. Its functions include protection, absorption, and secretion.
• Nerve tissue: Transmits electrical signals. Functions include the creation and transmission of electrical impulses from the nervous system to target organs. For example, the brain sends signals to skeletal muscles through nerves, enabling muscle contraction and movement.
• Connective tissue: Comprises collagen, providing strength via resistance to stretching. Contains elastin, characterized by flexibility and enabling easy bending and stretching.
  • Connective tissue proper: Includes tendons linking muscles to bones, ligaments stabilizing joints, capsules enclosing joints with outer fibrous layers, and inner synovial layers secreting lubricating fluid. Fascia that binds with multiple muscles helps connect multiple muscles together
  • Specialized connective tissue: Includes cartilage and bone, providing a flexible and strong framework for the body.
• Muscle tissue: Facilitates movement and various bodily functions.

Connective Tissue Types

• Tendon: Connects muscle to bone, primarily composed of collagen fibers.
• Ligament: Connects bone to bone, stabilizing the joint.
• Capsule: Encloses joints, featuring an outer fibrous layer and an inner synovial layer that secretes lubricating fluid to reduce friction.
• Fascia: Wraps around and connects multiple muscles.

Specialized Connective Tissue Details:

• Cartilage tissue: Cartilage tissue has three types - hyaline cartilage, fibrocartilage, and elastic cartilage.
  • Hyaline cartilage: Most common type. Its location is in embryonic bones, the trachea to allow airflow to the lungs, the front of the ribs, and the ends of bones in a joint to reduce friction.
  • Fibrocartilage: Includes hyaline cartilage and is a combination of collagen to provide durability to the elastic tissue. Annulus fibrosus is found in intervertebral discs, and Meniscus is within the knee joint.
  • Elastic cartilage: Hyaline cartilage with collagen and elastin. It is in the earlobe, auditory tube, and nose.
• Bone tissue: Bone tissue has multiple functions. It enables the grip of the muscles, gives the body its shape, protects its internal structures, allows the creation of blood cells, and contains a multitude of calcium.
  • Osteoblast (Young Bone Cell): Bone-forming cells responsible for synthesizing bone tissue.
  • Osteocytes (Mature Bone Cells): Mature bone cells responsible for the maintenance of bone tissue.
  • Osteoclast: (Decomposing Bone Cell): Cells that break down collagen and calcium.

Bone Structure:

• Diaphysis: The main, central part of the bone, providing strength.
• Epiphysis: The ends of the bone, composed of spongy tissue.
• Articular Cartilage: Covers the ends of the bone, providing a smooth surface for joint movement.
• Marrow: Located in the central cavity of the bone.
• Epiphyseal Plate: Area of growth.

Types of bone tissue

• Spongy bone contributes to the internal section of the bone's ends and contains a porous structure.
• Compact bone creates the rigid external section of the bone providing body support.

Types of Bones:

• Long bones: Act as levers for movement, located in limbs like arms, legs, fingers, and toes.
• Flat bones: Provide protection, located in the pelvis, scapula, ribs, skull, and sternum.
• Short bones: Located in the wrist and ankle.
• Irregular bones: Located in the vertebrae and facial bones. Function to add support to the body.
• Sesamoid bones: Located within the tendon, used as the patella.

Process of Endochondral Ossification:

• A cartilaginous model forms shaped like the future bone.
• Primary ossification center develops bone collar around the diaphysis. Osteoblasts start to produce bone material, and cartilage cells deteriorate.
• Bone growth extends from the diaphysis towards the epiphyses.
• Secondary- Similar starts in the epiphyses.
• An epiphyseal growth plate develops between the diaphysis and epiphyses, allowing further bone lengthening.
• Formation of the epiphyseal line indicates the end of bone growth.

Muscle Tissue:

• Muscle tissue moves body parts, such as limbs and the spine. It is an essential tissue in functioning the internal structures, such as moving food to the intestines through the muscle. This tissue makes up cells that contract.
  • Striated Muscle
  • Smooth Muscle is found in internal structures

Striated Muscle:

• Skeletal muscle hooks to bones and supports their movement
• Cardiac muscle, a mix of striated and smooth muscle, is found in internal structures.

Macroscopic Structure of Skeletal Muscle:

• Sarcomere: The basic unit of skeletal muscle.
• Myofibril: A long line of sarcomeres.
• Muscle Fiber: Collection of myofibrils.
• Fascicle: Bundle of muscle fibers.
• Muscle: Collection of fascicles.

Sarcomere:

• Myofibrils are Intracellular square units with the proteins. It is the basic contractile unit of muscle tissue. It has two proteins:
  • Thin Protein has the protein molecule Actin, Troponin, Tropomyosin
  • Thick Protein has the protein molecule Myosin

Process of Muscle Contraction:

• During contraction, myosin heads extend and bind to actin, pulling it inward.
• The overlap between proteins increases, and the sarcomere shortens.
  • A nerve stimulation leads to the creation of Myosin heads
  • The Myosin heads connects to the Actin
  • A motion of the myosin heads to the middle of the sarcomere slides the actin toward the middle
  • The motion will happen repeatedly till the actin and myosin perfectly connects