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HUMAN BODY SYSTEMS

Unit 8: Biological Systems

RESPIRATORY SYSTEM

Structures of the Respiratory System

The respiratory system is crucial for allowing gas exchange between the external environment and the blood. The following structures are integral components:

  • Nasal Cavity: The hollow space behind the nose that filters, warms, and moistens air as it enters the body.
  • Nostril: The external openings of the nasal cavity where air enters.
  • Soft Palate: The back part of the roof of the mouth that helps in swallowing.
  • Hard Palate: The front portion of the roof of the mouth that separates the nasal cavity from the oral cavity.
  • Oral Cavity: The mouth region where the mechanical processing of food occurs.
  • Larynx: Also known as the voice box, located at the upper part of the trachea, it houses the vocal cords.
  • Trachea: Commonly referred to as the windpipe, it is a sturdy tube reinforced with C-shaped cartilaginous rings, serving as the main airway connecting the larynx to the bronchi. It is lined with mucus and cilia, which trap and sweep away debris.
  • Carina of Trachea: The ridge at the base of the trachea that divides it into the right and left main bronchi.
  • Bronchi: The two main branches that split from the trachea, leading into each lung, branching further into smaller bronchioles.
  • Pharynx: The throat area that serves both respiratory and digestive systems.
  • Alveoli: Tiny, balloon-like air sacs at the ends of the bronchioles where gas exchange occurs. Oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled.
  • Diaphragm: A large, dome-shaped muscle located at the base of the lungs, responsible for breathing mechanics. It contracts to create a vacuum that pulls air into the lungs and relaxes to push air out.
  • Pharyngeal Tonsil: Also known as adenoids, located in the nasopharynx, playing a role in immune function.
  • Left and Right Lungs: Organs of respiration that house the bronchi, bronchioles, and alveoli. Their surface area is approximately the size of a tennis court, facilitating maximum gas exchange.

Functions of the Respiratory Structures

Conductors (Airways)
  • Glottis: The opening between the vocal cords that affects voice modulation through expansion and contraction.
  • Epiglottis: A leaf-shaped flap of cartilage located at the base of the tongue that protects the windpipe during swallowing, preventing food and liquid from entering the lungs.
  • Larynx: Positioned between the pharynx and the trachea and houses the vocal cords while providing protection to the lower airways and serving as the primary organ for sound production.
  • Bronchi: The main branches of the trachea that further divide into bronchioles, distributing air throughout the lungs.
Facilitators (Gas Exchange & Mechanics)
  • Alveoli: The functional units of the lungs where gas exchange takes place; oxygen passes into the blood while carbon dioxide is expelled.
  • Diaphragm: Functions as the main muscle in breathing, contracting to draw air into the lungs and relaxing to expel air.
  • Lungs: Serve as the primary organs in the respiratory process. Their vast surface area allows efficient oxygenation of the blood and removal of waste gases.

CIRCULATORY SYSTEM

Overview

The circulatory system is responsible for transporting gases, nutrients, and wastes throughout the body. It includes various blood vessels and is crucial for maintaining homeostasis.

  • Common Carotid Artery: Supplies blood to the head and neck.
  • Internal Jugular Vein: Drains blood from the brain.
  • Subclavian Artery: Supplies blood to the arms.
  • Axillary Artery: Continuation of the subclavian artery supplying blood to the axilla and upper limb.
  • Superior Vena Cava: Returns deoxygenated blood from the upper body to the right atrium of the heart.
  • Pulmonary Vein: Carries oxygenated blood from the lungs to the left atrium.
  • Inferior Vena Cava: Returns deoxygenated blood from the lower body to the heart.
  • Pulmonary Artery: Transports deoxygenated blood from the right ventricle to the lungs.
  • Aorta: The largest artery in the body, originating from the left ventricle, serves as the main exit for oxygenated blood to the body.

Heart Structures & Functions

  • Right & Left Atrium: The receiving chambers of the heart.
      - Right Atrium: Receives deoxygenated blood from the body via the vena cava.
      - Left Atrium: Receives oxygenated blood from the lungs.

  • Right & Left Ventricle: The pumping chambers of the heart, with thicker muscular walls.
      - Right Ventricle: Pumps deoxygenated blood to the lungs for gas exchange.
      - Left Ventricle: The strongest chamber, pumps oxygenated blood to the entire body.

Protective Structures

  • Pericardium: A tough, double-layered sac enclosing the heart. It protects the heart, anchoring it in the chest while providing lubrication to prevent friction as the heart beats.
  • Septum: The thick muscular wall separating the left and right sides of the heart, preventing mixing of oxygenated and deoxygenated blood.

Blood Vessel Types

  • Arteries: Blood vessels that carry blood away from the heart, characterized by thick, elastic walls suited for high-pressure situations.
  • Veins: Blood vessels that carry blood back to the heart, having thinner walls and valves to prevent backflow.

Blood Pathway (Flow)

The Pulmonary Circuit (Getting Oxygen)
  1. Deoxygenated blood enters the Right Atrium via the Vena Cava.
  2. It flows into the Right Ventricle.
  3. The Right Ventricle pumps it through the Pulmonary Artery to the Lungs.
  4. In the lungs, blood releases carbon dioxide (CO2) and takes on oxygen (O2).
The Systemic Circuit (Delivering Oxygen)
  1. Oxygenated blood returns to the Left Atrium via the Pulmonary Veins.
  2. It flows into the Left Ventricle.
  3. The Left Ventricle pumps it into the Aorta.
  4. The Aorta branches into smaller arteries, delivering oxygen to the body tissues.
  5. Deoxygenated blood returns to the heart through veins.

MUSCULAR SYSTEM

Major Muscles

The muscular system is responsible for allowing and creating movement through various types of muscles:

  • Trapezius
  • Deltoid
  • Pectoralis Major
  • Biceps Brachii
  • Rectus Abdominis
  • Brachialis
  • External Oblique
  • Brachioradialis
  • Finger Flexors
  • Infraspinatus
  • Teres Major
  • Triceps Brachii
  • Latissimus Dorsi
  • Finger Extensors
  • Adductor Longus
  • Gracilis
  • Sartorius
  • Rectus Femoris
  • Vastus Lateralis
  • Vastus Medialis
  • Gluteus Maximus
  • Semitendinosus
  • Biceps Femoris
  • Semimembranosus
  • Tibialis Anterior
  • Gastrocnemius
  • Soleus

Types of Muscles

Voluntary Muscles

Muscles that can be controlled at will, commonly known as skeletal muscles.

Involuntary Muscles

Muscles that operate automatically via the nervous system without conscious control.

Skeletal Muscles (Voluntary)

  • Attachment: Skeletal muscles are attached to bones via tendons.
  • Function: Facilitates body movement through voluntary actions like walking, lifting, and talking while maintaining posture.
  • Appearance: They are striated (striped) with long, cylindrical fibers containing multiple nuclei.
  • Location: Found throughout the body, prominently attached to the skeleton, e.g., biceps, quadriceps, deltoids.

Smooth Muscles (Involuntary)

  • Function: Moves substances through the body’s hollow organs, such as pushing food through the digestive tract and regulating blood flow in vessels.
  • Appearance: Non-striated and spindle-shaped, containing a single nucleus in the center of each cell.
  • Location: Present in walls of internal organs such as the stomach, intestines, bladder, and blood vessels.

Cardiac Muscles (Involuntary)

  • Function: Responsible for pumping blood throughout the body, contracting rhythmically.
  • Appearance: Striated like skeletal muscle, but with branched fibers and unique intercalated discs that aid in cell communication, allowing the heart to function as a single unit.
  • Location: Exclusively found in the walls of the heart.