Skeletal System: Structure and Function

• The skeletal system functions in support, movement, protection, blood cell production, mineral storage, and endocrine regulation.
• Red bone marrow produces blood cells, while yellow bone marrow stores fat.
• Periosteum is a fibrous connective tissue covering the bone, containing blood vessels and nerves.

Osteon Structure

• An osteon consists of concentric layers (lamellae) of compact bone tissue surrounding a central canal (Haversian canal) containing blood vessels and nerves.
• Canaliculi are small channels connecting lacunae, allowing nutrients and waste to be exchanged between osteocytes.

Long Bone Anatomy

• The parts of a long bone include the diaphysis (shaft), epiphyses (ends), metaphyses (where diaphysis and epiphyses meet), articular cartilage, periosteum, medullary cavity (containing bone marrow), and endosteum (lining the medullary cavity).
• Hyaline cartilage is found on the articular surfaces (ends) of long bones, providing a smooth surface for joint movement.
• Bones heal faster than cartilage due to a rich blood supply, which cartilage lacks.

Bone Remodeling and Calcium Regulation

• Bones regulate blood calcium levels through bone remodeling.
• Osteoblasts build bone and store calcium.
• Osteoclasts break down bone and release calcium into the bloodstream.

Hormones in Bone Remodeling

• Hormones involved in bone remodeling include parathyroid hormone (PTH), calcitonin, and vitamin D.
• PTH increases blood calcium levels by stimulating osteoclasts.
• Calcitonin lowers blood calcium levels by inhibiting osteoclasts.
• Vitamin D promotes calcium absorption in the intestine.

Bone Repair Steps

• Bone repair involves hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.
• The hyoid bone does not articulate with any other bone.

Hyoid Bone

• The hyoid bone is part of the axial skeleton.
• The ribs articulate with the thoracic vertebrae.
• Fibrocartilage is found between the vertebrae (intervertebral discs).

Major Skull Bones

• Major bones of the skull include the frontal, parietal, temporal, occipital, ethmoid, and sphenoid bones.
• The zygomatic bone forms the cheek.
• The pelvic girdle consists of the ilium, ischium, and pubis bones.
• The pectoral girdle consists of the clavicle and scapula bones.
• The upper arm contains the humerus, and the forearm contains the radius and ulna.
• The thigh contains the femur, and the shin contains the tibia and fibula.
• Finger bones are called phalanges, and toe bones are also called phalanges.
• A fibrous joint can be found in the sutures of the skull.

Synovial Joints

• Synovial joints are highly movable joints that contain a joint capsule, synovial membrane, synovial fluid, and articular cartilage.
• Examples include the knee, elbow, and shoulder joints.

Joint Movements

• Flexion decreases the angle between bones, while extension increases the angle.
• Adduction moves a body part toward the midline, while abduction moves it away.
• Inversion turns the sole of the foot inward, while eversion turns it outward.

Muscle Tissue Types

• Smooth muscle is found in the walls of internal organs and is involuntary.
• Cardiac muscle is found in the heart and is involuntary.
• Skeletal muscle is attached to bones and is voluntary.

Muscle Tissue Functions

• Smooth muscle functions in regulating blood pressure, digestion, and other involuntary processes.
• Cardiac muscle functions in pumping blood.
• Skeletal muscle functions in movement, posture, and heat generation.
• Muscles are attached to bones by tendons.
• The antagonistic muscle pair of the upper arm is the biceps brachii (flexor) and triceps brachii (extensor).

Muscles Named

• Muscles named by shape include the deltoid (triangle) and trapezius (trapezoid).
• Muscles named by size include the gluteus maximus (large) and gluteus minimus (small).
• Muscles named by location include the temporalis (near the temporal bone) and frontalis (near the frontal bone).
• Muscles named by number of insertions include the biceps brachii (two heads) and triceps brachii (three heads).
• The insertion of a muscle is on the moving bone.

Sternocleidomastoid Naming

• The sternocleidomastoid muscle is named by its origin points: the sternum, clavicle, and mastoid process of the temporal bone.
• The functional unit of skeletal muscle is the sarcomere.
• Calcium ions and ATP molecules are necessary for muscle contraction.
• At the neuromuscular junction, a neuron releases acetylcholine, which stimulates the muscle fiber.
• Muscles with many nerves controlling them allow for finer motor control.
• When a muscle is stimulated to maximum contraction it is called tetanus.
• A muscle cannot stay in a state of tetanus indefinitely due to fatigue.

Muscle Fibers

• Fast-twitch muscle fibers contract quickly and fatigue rapidly, while slow-twitch muscle fibers contract slowly and have high endurance.
• The central nervous system (CNS) consists of the brain and spinal cord.
• The skeletal system protects the central nervous system.

Neuron Structure

• The parts of a neuron include the cell body, dendrites, axon, and axon terminals.
• Impulses travel from the dendrites, through the cell body, down the axon, to the axon terminals.

Neuron Processes

• Depolarization occurs when the inside of the neuron becomes more positive due to influx of sodium ions.
• Repolarization occurs when the inside of the neuron becomes more negative due to outflow of potassium ions.
• Hyperpolarization (refractory period) is when the neuron is temporarily more negative than its resting state, making it difficult to initiate another action potential.
• Myelin and the nodes of Ranvier speed up the action potential by allowing it to "jump" along the axon through saltatory conduction.
• Integration is the process by which a neuron sums up all the incoming signals to determine whether or not to fire an action potential.

Brain Components

• The parts of the brain include the cerebrum, cerebellum, diencephalon (thalamus and hypothalamus), and brainstem.
• The cerebrum is responsible for higher-level cognitive functions.
• The cerebellum coordinates movement and balance.
• The thalamus relays sensory information.
• The hypothalamus regulates body temperature, hunger, and thirst.
• The brainstem controls basic life functions, like breathing and heart rate.

Brain Lobes

• The lobes of the brain are the frontal, parietal, temporal, and occipital lobes.
• The frontal lobe is involved in planning, decision-making, and motor control.
• The parietal lobe processes sensory information.
• The temporal lobe is involved in hearing and memory.
• The occipital lobe processes visual information.

Limbic System

• The limbic system is involved in emotions, memory, and motivation.
• The parts of the brainstem include the midbrain, pons, and medulla oblongata.
• The thalamus receives all sensory input except for smell.
• The primary motor area is responsible for voluntary movement.
• Primary somatosensory area receives information about touch, temperature, pain, and pressure.

Memory

• Short-term memory is temporary storage of information.
• Long-term memory is the relatively permanent storage of information.
• Skill memory is memory for how to perform tasks.
• Semantic memory is memory for facts and general knowledge.
• Episodic memory is memory for personal experiences.

Hippocampus

• The hippocampus forms new memories.

Nervous System

• The sympathetic nervous system is responsible for the "fight or flight" response.
• The parasympathetic nervous system is responsible for the "rest and digest" response.
• Ventilation is the process of moving air in and out of the lungs.
• Inspiration is the process of bringing air into the lungs.
• Expiration is the process of moving air out of the lungs.

Respiratory System Functions

• The functions of the respiratory system include gas exchange, regulation of blood pH, voice production, and protection against inhaled pathogens.

Upper Respiratory Tract

• The parts of the upper respiratory tract include the nose, nasal cavity, pharynx, and larynx.
• The nose filters, warms, and humidifies air.
• The pharynx is a passageway for air and food.
• The larynx contains the vocal cords.

Lower Respiratory Tract

• The parts of the lower respiratory tract include the trachea, bronchi, bronchioles, and alveoli.
• The brainstem (specifically the medulla oblongata and pons) controls respiration.
• The diaphragm is the primary muscle involved in respiration.
• The diaphragm is made of skeletal (though involuntary) muscle.
• The larynx participates in the production of sound.
• The cardiovascular and respiratory systems meet at the alveoli in the lungs.
• Goblet cells in the trachea secrete mucus to trap debris and pathogens.
• Oxygen moves from the alveoli into the blood.
• Carbon dioxide moves from the blood into the alveoli.
• Holding your breath is initially voluntary, but eventually involuntary mechanisms will take over.