Oblique Muscles

Muscles of the abdomen aiding trunk rotation.

Anatomy

Obsessive-Compulsive Disorder (OCD)

Anxiety disorder with intrusive thoughts and repetitive behaviors.

Psychology

Obturator Internus

Hip muscle aiding external rotation.

Anatomy

Occipital Bone

Skull bone at the back of the head.

Anatomy

Occipital Lobe

Brain lobe responsible for vision.

Neuroscience

Occiput

Posterior part of the skull.

Anatomy

Occlusion

Closure or blockage of a vessel or airway.

Pathophysiology

Olfaction

Sense of smell.

Physiology

Olfactory Bulb

Brain structure processing smell.

Anatomy

Oligodendrocyte

Glial cell forming CNS myelin.

Neuroscience

Oligosaccharide

Carbohydrate with 3–10 sugar units.

Chemistry / Nutrition

Oliguria

Low urine output.

Pathophysiology

Omega-3 Fatty Acids

Essential polyunsaturated fats promoting heart health.

Nutrition

Omega-6 Fatty Acids

Essential polyunsaturated fats involved in inflammation.

Nutrition

Oncogene

Mutated gene promoting uncontrolled cell growth.

Genetics / Pathophysiology

Onset of Blood Lactate Accumulation (OBLA)

Exercise intensity where lactate builds rapidly.

Exercise Physiology

Open Chain Exercise

Movement with distal limb free to move.

Biomechanics / Exercise Prescription

Open Reduction

Surgical repair of a fracture with exposure of bone.

Medicine / Sport Injury

Ophthalmology

Study of the eye and vision disorders.

Medicine

Opioid

Drug class binding opioid receptors for pain relief.

Medicine / First Aid

Opportunistic Infection

Infection occurring in weakened immune systems.

Pathophysiology

Optic Chiasm

Crossing point of optic nerves.

Anatomy

Optic Nerve

Cranial nerve transmitting visual signals.

Anatomy

Optimum Arousal Theory

Performance peaks at moderate arousal.

Sport Psychology

Oral Cavity

Mouth as entry point for digestion.

Anatomy

Oral Rehydration Therapy (ORT)

Fluid replacement treatment for dehydration.

First Aid / Medicine

Orbicularis Oculi

Muscle closing the eyelids.

Anatomy

Orbicularis Oris

Muscle controlling mouth movements.

Anatomy

Orbit (Eye Socket)

Bony cavity housing the eyeball.

Anatomy

Organ

Structure composed of tissues performing a function.

Anatomy

Organ of Corti

Inner ear sensory organ for hearing.

Physiology

Organelle

Specialized cell structure with specific function.

Biology

Organic Compound

Molecule containing carbon.

Chemistry

Origin (Muscle)

Fixed attachment point of a muscle.

Anatomy

Orthopedics

Medical specialty for bones/joints/muscles.

Medicine

Orthopnea

Difficulty breathing while lying down.

Pathophysiology

Orthostatic Hypotension

Drop in blood pressure upon standing.

Pathophysiology

Osteoarthritis

Degenerative joint disease with cartilage breakdown.

Pathophysiology

Osteoblast

Bone-forming cell.

Biology

Osteoclast

Bone-resorbing cell.

Biology

Osteocyte

Mature bone cell maintaining tissue.

Biology

Osteogenesis

Process of bone formation.

Physiology

Osteomalacia

Softening of bones due to vitamin D deficiency.

Pathophysiology

Osteomyelitis

Bone infection.

Pathophysiology

Osteon

Structural unit of compact bone.

Anatomy

Osteopenia

Reduced bone density, precursor to osteoporosis.

Pathophysiology

Osteophyte

Bone spur formation at joints.

Pathophysiology

Osteoporosis

Condition of low bone density, fracture risk.

Pathophysiology

Osteosarcoma

Malignant bone tumor.

Pathophysiology

Osteotomy

Surgical cutting of bone.

Medicine

Otitis Externa

Infection of outer ear canal.

Pathophysiology

Otitis Media

Infection of middle ear.

Pathophysiology

Otolith Organs

Inner ear structures sensing balance and acceleration.

Physiology

Otorhinolaryngology (ENT)

Medical specialty of ear, nose, throat.

Medicine

Outcome Measure

Standard used to assess treatment effects.

Exercise Testing

Ovary

Female reproductive organ producing eggs and hormones.

Anatomy

Overload Principle

Training concept of progressively increasing demands.

Strength & Conditioning

Overpronation

Excessive inward roll of foot during gait.

Biomechanics

Overtraining Syndrome

Condition of chronic fatigue and reduced performance.

Exercise Physiology

Ovulation

Release of egg from ovary.

Physiology

Oxidation

Chemical reaction involving electron loss.

Chemistry

Oxidative Phosphorylation

ATP production in mitochondria using oxygen.

Physiology

Oxidative Stress

Cellular damage from free radicals.

Pathophysiology

Oximeter

Device measuring blood oxygen saturation.

Medicine / Exercise Testing

Oxygen Consumption (VO₂)

Volume of oxygen used by body.

Exercise Physiology

Oxygen Debt

Extra oxygen needed after exercise for recovery.

Physiology

Oxygen Deficit

Delay in oxygen uptake at exercise onset.

Exercise Physiology

Oxygen Saturation (SpO₂)

Percentage of hemoglobin bound with oxygen.

Physiology

Oxygen Uptake Kinetics

Rate of adjustment in oxygen use during exercise.

Exercise Physiology

Oxyhemoglobin

Hemoglobin bound to oxygen.

Physiology

Oxyhemoglobin Dissociation Curve

Relationship between oxygen binding and release.

Physiology

Oxyntic Cells (Parietal Cells)

Stomach cells secreting acid.

Physiology

Oxytocin

Hormone regulating childbirth and bonding.

Physiology

Ozaki Procedure

Heart valve reconstruction technique.

Medicine

Ozone Therapy

Alternative therapy using ozone gas.

Medicine (Alternative)