Skeletal Muscle Structure and Function

• The structure of skeletal muscle includes bundles of bundles, starting with the muscle itself, which is a bundle of fascicles.
• Fascicles are bundles of muscle fibers, which are bundles of myofibrils, and myofibrils are bundles of myofilaments.
• Tendons attach muscle to bone.

Function of Skeletal Muscle

• Skeletal muscles provide support, facilitate voluntary movement, and offer protection.
• Skeletal muscles contribute to temperature homeostasis.

Muscle Twitch and Summation

• A muscle twitch is one cycle of contraction and complete relaxation and is not very useful on its own.
• Summation is multiple contractions without complete relaxation, enabling useful, controlled movements.

Fast Twitch Fibers

• Fast twitch fibers use little oxygen and rely on anaerobic processes.
• They are larger and more powerful but fatigue quickly.

Slow Twitch Fibers

• Slow twitch fibers are aerobic and use oxygen.
• They provide steady power and endurance.

Muscle Actions

• Synergists assist the prime mover to make an action more effective.
• Muscle tone is light contractions that create firm movement.
• The antagonist is the muscle that restricts movement.
• The prime mover is the main muscle involved in a movement.

Muscle Components

• Myosin is the thick filament involved in muscle contraction.
• Actin is the thin filament, resembling a strand of pearls.
• The sarcomere is the space between two "z lines" and is the functional unit of muscle contraction, "z lines" are pulled together during contraction.

Motor Units and Recruitment

• A motor unit consists of all muscle fibers controlled by a single neuron.
• Recruitment is the process of adding motor units to accomplish a movement.

Muscle Attachment Points

• The origin of a muscle does not change position during contraction.
• The insertion of a muscle changes position during contraction.

Fitness and Tetanus

• Fitness is the ability to perform an activity for a long period.
• Tetanus is a contraction without relaxation until muscle fatigue.

Accessory Organs of Skin

• Accessory organs of the skin include nails, hair follicles, and exocrine glands (oil and sweat glands).

Membranes

• Mucous membranes line tubes that lead in and out of the body and are involved in secretion.
• Synovial membranes line moveable joint cavities and secrete fluid to reduce friction.
• Serous membranes line ventral body cavities.
• Meninges line dorsal cavities.
• Cutaneous membrane refers to the skin.

Body Cavities

• Dorsal cavities include cranial and vertebral cavities.
• Ventral cavities include thoracic, abdominal, and pelvic cavities.

Skin Layers

• The subcutaneous layer (hypodermis) is the bottom layer of skin and contains adipose tissue.
• The dermis is the middle layer of skin, consisting of loose fibrous tissue and containing most accessory organs.
• The epidermis is the top layer of skin and is made of stratified squamous epithelial tissue.

Skin Coloration

• Melanocytes produce melanin in the bottom layer of the epidermis.

Skin Cancer Types

• Melanoma starts in melanocytes, divides uncontrollably, spreads via blood vessels, and is dangerous.
• Basel cell carcinoma starts at the bottom of the epidermis and is the easiest to heal.

Skin Repair Steps

• The steps in skin repair are: blood clotting, epidermal cells migrating into the wound, white blood cells attacking invaders, scab formation, epidermal cells completing the cover, and fibroblasts smoothing out skin.

Integumentary System Function

• The integumentary system (skin) provides a protective covering, contributes to temperature homeostasis, and is involved in vitamin D synthesis.

Axial Skeleton

• The axial skeleton includes the skull, vertebral column, sacrum, coccyx, and ribcage

Appendicular Skeleton

• The appendicular skeleton includes the arms, legs, and girdles that attach them to the axial skeleton.

Spongy Bone

• Spongy bone is the third layer of long bone that has an irregular pattern and contains red bone marrow, where red blood cells are made.

Ossification

• Ossification is the process where connective tissue is turned into bone.

Joint Strength vs. Movement

• The greater the movement a joint allows, the weaker it is, and vice versa.

Body Movement Types

• Rotation is a body part moving around its own axis.
• Circumduction is cone-shaped movement.
• Abduction is a body part moving away from the midline.
• Adduction is a body part moving toward the midline.
• Flexion decreases the angle of a joint.
• Extension increases the angle of a joint.

Bone Remodeling

• Bone remodeling involves adding and subtracting bone material continuously.
• Osteoblasts are immature bone cells that add bone material.
• Osteoclasts are cells that break down bone material.

Ossification Types

• Intramembranous ossification occurs in sheets of fibrous connective tissue, forming the skull, jaw, and clavicle.
• Endochondral ossification starts as hyaline cartilage and forms all other bones.

Bone Growth Area

• The epiphyseal plate is the site of bone lengthening.

Factors Increaseing Bone Length

• Growth hormone, thyroid hormone, vitamin D, and calcium all contribute to increasing bone length.

Functions of Skeletal System

• The functions of the skeletal system include support, movement, protection, blood cell production, and mineral and fat storage.

Skeletal System Structure

• The skeletal system consists of bones, joints, and ligaments.

Periosteum

• The first layer of long bone is the periosteum, which consists of fibrous connective tissue and is continuous with tendons and ligaments.

Bone Repair Steps

• Bone repair involves hematoma formation, fibrocartilaginous callus formation (fibrous connective tissue and hyaline cartilage), bony callus formation (osteoblasts and osteoclasts), and bone remodeling.

Compact Bone

• The second layer of long bone is compact bone, which provides compressive support.
• Osteocytes are mature bone cells surrounded by ground substance.
• Central canals transport nutrients.
• Osteons provide support.

Articulations Types

• Articulations, or joints, include sutures with little to no movement and synovial joints with a lot of movement.

Tissue

• Epithelial tissue covers surfaces and provides protection.

Cell Types

• Squamous cells are flat and pancake-like.
• Cuboidal cells are squared.
• Columnar cells are rectangular and long.

Tissue Layer Types

• Simple tissues are one cell layer thick and are involved in absorption and excretion.
• Stratified tissues are two or more cell layers thick and provide protection.
• Pseudostratified columnar epithelium appears stratified but is simple.

Tissue Function

• Simple squamous epithelium protects and lines the lungs and blood vessels; it is involved in absorption and excretion.
• Simple cuboidal epithelium absorbs and excretes and is found in the lining of kidney tubes.
• Simple columnar epithelium absorbs nutrients and lines the small intestine.
• Stratified squamous epithelium protects and lines the esophagus.
• Pseudostratified ciliated columnar epithelium lines the trachea and is involved in absorption and excretion.
• Dense fibrous connective tissue connects muscles to bones (ligaments) and is found in tendons (connect bone to bone).
• Hyaline cartilage is found at the ends of bones and reduces friction.
• Loose fibrous connective tissue supports and protects organs such as the lungs, arteries, and urinary bladder.
• Adipose tissue provides insulation and is found in the bottom layer of skin.
• Connective tissue binds other tissues together
• Muscle tissue role is movement
• Neural tissue sends electric signals

Types of Muscle Tissue

• Skeletal muscle tissue is long and cylindrical, has multiple nuclei and striations, and allows for voluntary movement.
• Smooth muscle tissue is spindle-shaped, has no striations, has one nucleus, and facilitates the movement of substances.
• Cardiac muscle tissue is Y-shaped, has one nucleus and striations.

Connective Tissue Elements

• The main elements of connective tissue include specialized cells, ground substance, and various protein fibers.

Fibrous Connective Tissue Function

• Fibrous connective tissue creates a loose, open framework or densely packed fibers.
• The types of connective tissue are: Fibrous Supportive Fluid

Tissue Support Types

• Supportive connective tissue has a solid yet flexible matrix (cartilage) and a solid and rigid matrix (bone).
• Fluid connective tissue is contained in blood vessels and lymphatic vessels.

Nervous Tissue Components

• Neurons are the cells of nervous tissue.
• Nerves are bundles of neurons.
• Neuroglia are cells that support neurons.

Explore the hierarchical structure of skeletal muscle, from muscle bundles to myofilaments. Learn about muscle's role in support, movement, protection, and temperature regulation. Understand muscle twitches, summation, and the different properties of fast and slow twitch fibers.