Human Eye Anatomy and Function

Human Eye

• Light Pathway: Light enters the eye, passes through a converging lens, and strikes the retina where the image is formed and processed.
• Accommodation: The eye adjusts the lens's shape to focus. A near object causes the lens to widen, while a distant object makes the lens thinner. This allows for better focus at varying distances.
• Vision Diseases:
  • Hyperopia (Farsightedness): Distant objects are seen clearly, but close objects appear blurry. The image focuses behind the retina. Presbyopia is a type of farsightedness caused by age-related lens hardening.
  • Myopia (Nearsightedness): Distant objects cannot be seen clearly. The image focuses in front of the retina.

Eye Anatomy

• Cornea: Transparent layer covering the front of the eye.
• Iris: Colored, ring-shaped membrane behind the cornea.
• Pupil: Opening in the center of the iris that allows light to enter the eye.
• Retina: Layer of cells inside the eye that detect light.
• Lens: Converging lens within the eye, responsible for focusing light onto the retina.
• Optic Nerve: Transmits impulses from the light in the eye to the brain to generate an image.

Digestive System

• Organs (Tract):
  • Mouth: Digestion begins here.
  • Esophagus: Transports food from the mouth to the stomach through peristalsis (involuntary muscle contractions).
  • Stomach: Continues digestion.
  • Small Intestine: Further breaks down food, absorbs nutrients.
  • Large Intestine: Absorbs water and forms feces.
  • Anus: Eliminates waste.
• Accessory Organs:
  • Salivary Glands: Produce saliva to aid in digestion.
  • Pancreas: Produces insulin to regulate blood glucose.

Respiratory System

• Function: Supplies oxygen to the body and removes carbon dioxide.
• Mechanism: Oxygen enters via diffusion, and carbon dioxide exits the same way.
• Alveoli: Tiny air sacs in the lungs with capillaries for gas exchange.
• Inhalation: Diaphragm contracts, pushing air into the lungs.
• Exhalation: Diaphragm expands, pushing air out of the lungs.
• Cellular Respiration: Glucose + Oxygen → Carbon Dioxide + Water + Energy.

Nervous System

• Function: Senses the environment and signals the body to respond.
• Parts:
  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): Nerves that carry signals between the CNS and the body.
• Nerve Tissue: Specialized cells that transmit impulses.
  • Afferent Nerves: Sensory nerves; detect stimuli.
  • Efferent Nerves: Motor nerves; trigger responses in muscles.
• Brain Lobes:
  • Frontal Lobe: Thinking, memory, behavior, and movement.
  • Parietal Lobe: Language and touch.
  • Temporal Lobe: Hearing, learning, and feelings.
  • Occipital Lobe: Sight.
  • Cerebellum: Balance and coordination.
  • Brain Stem: Breathing, heart rate, and temperature.

Blood

• Red Blood Cells: Carry oxygen using hemoglobin, delivering it to tissues.
• White Blood Cells: Fight infection.
• Platelets: Help blood clot to stop bleeding.
• Plasma: Liquid part of blood carrying nutrients, hormones, and waste products.

Circulatory System

• Heart Chambers:
  • Atria (2): Receiving chambers.
  • Ventricles (2): Discharging chambers.
• Blood Vessels:
  • Arteries: Carry blood away from the heart.
  • Veins: Carry blood toward the heart.
  • Capillaries: Connect arteries and veins.
• Circulatory Systems:
  • Pulmonary: Carries oxygen-poor blood to the lungs for oxygenation.
  • Systemic: Carries oxygen-rich blood to the body.
• Heart Valves:
  • Tricuspid Valve
  • Pulmonary Valve
  • Mitral Valve
  • Aortic Valve
• Right side of heart pumps oxygen-poor blood to the lungs, Left side pumps oxygen-rich blood to the body.

Musculoskeletal System

• Bone: Connective tissue providing structure and support.
• Ligaments: Connective tissue connecting bones.
• Cartilage: Connective tissue in joints, ears, and nose.
• Tendons: Connective tissue connecting muscles to bones.
• Voluntary Movement: Muscles under conscious control.
• Involuntary Movement: Muscles not under direct control. Muscle fibers contract when stimulated, exerting force and moving connected parts.

Cell Structure (Plant vs. Animal)

• Cell Membrane: Controls what enters and exits the cell.
• Nucleus: Control center of the cell, containing DNA.
• Cytoplasm: Jelly-like fluid where cell processes occur.
• Mitochondria: Produce energy.
• Ribosomes: Make proteins.
• Cell Wall (Plant Cells Only): Provides structure and support.
• Chloroplasts (Plant Cells Only): Use sunlight to make food (photosynthesis).
• Vacuole: Storage in both, but maintains water balance in plant cells and sequesters waste in animal cells.

Diffusion

• Movement of Particles: Particles move from areas of high concentration to low concentration.
• Example: In the lungs, oxygen diffuses from the air sacs (alveoli) into the blood because there's more oxygen in the alveoli than in the blood. Simultaneously, carbon dioxide moves from the blood to the alveoli to be exhaled.

Refraction (Calculating, Apparent Depth)

• Index of Refraction: (n = c/v). n = index of refraction, c = speed of light in a vacuum (constant 3.00 x 10⁸ m/s), v = speed of light in the medium.
• Apparent Depth: Objects in water appear closer to the surface than they actually are due to light refraction.

Lenses (Convex and Concave)

• Convex Lens:
  • Parallel rays refract through a focal point (F).
  • Rays through the center (O) continue straight.
• Concave Lens:
  • Parallel rays appear to refract through a focal point (F').
  • Rays through the center (O) continue straight. Image is smaller, upright and virtual.

Explore the intricate structure and functions of the human eye in this quiz. Learn about how light travels through the eye, the focusing mechanisms, and common vision diseases like hyperopia and myopia. Test your knowledge of eye anatomy, including parts such as the cornea, iris, and retina.