TExES Health EC-12 (257)

This section examines the foundational knowledge required for health educators to teach comprehensive health and wellness concepts across all grade levels. Topics include human body systems, physical fitness principles, mental and emotional health promotion, social health dynamics, and developmental changes throughout the lifespan. Mastery of these concepts enables educators to deliver accurate, age-appropriate instruction that supports student health literacy and positive health behaviors.

The human body is organized into hierarchical structural levels. Cells are the basic units of life, containing organelles that perform specific functions. Similar cells group together to form tissues. The four primary tissue types are epithelial (covering and lining), connective (support and protection), muscle (movement), and nervous (communication and control). Tissues combine to form organs, which are structures with specific functions. Organs work together in organ systems to maintain life processes.

Homeostasis is the body's ability to maintain a stable internal environment despite external changes. This dynamic equilibrium involves continuous monitoring and adjustment of temperature, pH, blood glucose, fluid balance, and other variables. Negative feedback loops are the primary mechanism for homeostasis, where a change triggers a response that reverses the change. Positive feedback loops amplify changes and are less common, occurring in processes like blood clotting and childbirth.

The skeletal system provides structural support, protection for internal organs, mineral storage, blood cell production, and leverage for movement. The adult skeleton contains 206 bones divided into the axial skeleton (skull, vertebral column, rib cage) and appendicular skeleton (limbs and girdles).

Bones are classified by shape as long (femur, humerus), short (carpals, tarsals), flat (skull bones, scapula), irregular (vertebrae), and sesamoid (patella). Bone tissue contains osteocytes (mature bone cells), osteoblasts (bone-forming cells), and osteoclasts (bone-resorbing cells). The continuous process of bone remodeling allows adaptation to stress and repair of damage.

Joints are classified by structure and movement capability. Fibrous joints (sutures) allow no movement. Cartilaginous joints (intervertebral discs) allow limited movement. Synovial joints allow free movement and include hinge (elbow), ball-and-socket (hip), pivot (atlas-axis), saddle (thumb), condyloid (wrist), and gliding (intercarpal) types.

Bone health depends on adequate calcium, phosphorus, and vitamin D intake; weight-bearing exercise; and hormonal balance. Peak bone mass is achieved by approximately age 30. Osteoporosis, characterized by decreased bone density and increased fracture risk, is preventable through lifestyle factors established during childhood and adolescence.

The muscular system enables movement, maintains posture, generates heat, and supports circulation. Three muscle types exist: skeletal (voluntary, striated, attached to bones), cardiac (involuntary, striated, heart wall), and smooth (involuntary, non-striated, internal organs and blood vessels).

Skeletal muscles work in antagonistic pairs. When one muscle contracts (agonist), the opposing muscle relaxes (antagonist). Major muscle groups include those of the head and neck, trunk (abdominals, back extensors), upper extremities (deltoids, biceps, triceps), and lower extremities (quadriceps, hamstrings, gastrocnemius).

Muscle contraction occurs through the sliding filament mechanism. Actin and myosin filaments slide past each other, shortening the sarcomere. This process requires calcium ions and ATP. Muscle fibers are classified as slow-twitch (Type I, endurance) and fast-twitch (Type II, power and speed).

Muscle fitness includes muscular strength (maximum force production), muscular endurance (sustained contractions), and flexibility (range of motion). Progressive overload, specificity, and recovery are principles for improving muscle fitness. Common muscular injuries include strains, sprains, and overuse injuries such as tendinitis.

The cardiovascular system transports oxygen, nutrients, hormones, and waste products throughout the body. Components include the heart (pump), blood vessels (conduits), and blood (transport medium).

The heart is a four-chambered muscular organ. The right atrium receives deoxygenated blood from the body via the superior and inferior vena cavae. Blood flows to the right ventricle, which pumps it to the lungs through the pulmonary arteries. Oxygenated blood returns via the pulmonary veins to the left atrium, then to the left ventricle, which pumps it to the body through the aorta.

The cardiac cycle consists of systole (contraction) and diastole (relaxation). The sinoatrial node initiates electrical impulses that coordinate heart contractions. Heart rate is influenced by the autonomic nervous system, hormones, temperature, and physical activity. Resting heart rate for adults is typically 60-100 beats per minute, while trained athletes may have lower rates.

Blood vessels include arteries (carry blood away from heart), arterioles, capillaries (gas and nutrient exchange), venules, and veins (return blood to heart). Blood pressure is the force of blood against vessel walls, expressed as systolic over diastolic pressure. Normal adult blood pressure is approximately 120/80 mmHg.

Blood components include plasma (55%), red blood cells (oxygen transport), white blood cells (immune function), and platelets (clotting). Blood types (A, B, AB, O) and Rh factor are determined by surface antigens on red blood cells.

Cardiovascular disease is the leading cause of death in the United States. Risk factors include hypertension, high cholesterol, smoking, diabetes, obesity, physical inactivity, and family history. Prevention focuses on lifestyle modifications including regular physical activity, healthy diet, maintaining healthy weight, avoiding tobacco, and managing stress.

The respiratory system facilitates gas exchange between the body and environment. Air enters through the nose or mouth, passes through the pharynx, larynx, trachea, bronchi, and bronchioles, and reaches the alveoli where gas exchange occurs.

The nose filters, warms, and humidifies inhaled air. The larynx contains the vocal cords and prevents food from entering the airway. The trachea branches into left and right primary bronchi, which further divide into secondary and tertiary bronchi, then bronchioles, and finally alveoli. Approximately 300 million alveoli provide a large surface area for gas exchange.

Ventilation is the mechanical process of breathing. Inspiration occurs when the diaphragm and intercostal muscles contract, increasing thoracic volume and decreasing pressure, causing air to flow in. Expiration is typically passive, occurring when muscles relax and elastic recoil decreases thoracic volume.

External respiration is gas exchange between alveoli and pulmonary capillaries. Internal respiration is gas exchange between systemic capillaries and body cells. Oxygen and carbon dioxide move by diffusion across concentration gradients.

Respiratory health threats include asthma (airway inflammation and constriction), chronic obstructive pulmonary disease (COPD), pneumonia, lung cancer, and respiratory infections. Tobacco smoke is the primary cause of preventable respiratory disease. Air quality, occupational exposures, and allergens also affect respiratory health.

The digestive system breaks down food into absorbable nutrients and eliminates waste. The alimentary canal extends from mouth to anus and includes the oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and rectum. Accessory organs include salivary glands, liver, gallbladder, and pancreas.

Mechanical digestion physically breaks food into smaller pieces through chewing and churning. Chemical digestion uses enzymes to break down macromolecules. Carbohydrate digestion begins in the mouth with salivary amylase. Protein digestion begins in the stomach with pepsin. Lipid digestion occurs primarily in the small intestine with pancreatic lipase and bile.

The small intestine is the primary site of nutrient absorption. Villi and microvilli increase surface area. Monosaccharides, amino acids, and water-soluble vitamins enter capillaries. Fatty acids and fat-soluble vitamins enter lacteals. The large intestine absorbs water and electrolytes, houses beneficial bacteria, and forms feces.

The liver performs numerous functions including bile production, nutrient metabolism, detoxification, and storage of vitamins and glycogen. The pancreas secretes digestive enzymes and bicarbonate into the small intestine and produces insulin and glucagon for blood glucose regulation.

Digestive disorders include gastroesophageal reflux disease (GERD), peptic ulcers, inflammatory bowel disease, celiac disease, and colorectal cancer. Healthy digestion is supported by adequate fiber intake, hydration, regular physical activity, and stress management.

The nervous system controls and coordinates body activities through electrical and chemical signals. It is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (cranial and spinal nerves).

Neurons are the functional units of the nervous system. They consist of a cell body, dendrites (receive signals), and axon (transmit signals). Synapses are junctions between neurons where neurotransmitters carry signals across the synaptic cleft. Major neurotransmitters include acetylcholine, dopamine, serotonin, norepinephrine, GABA, and glutamate.

The brain contains approximately 86 billion neurons. Major regions include the cerebrum (higher functions, divided into frontal, parietal, temporal, and occipital lobes), cerebellum (coordination and balance), and brainstem (vital functions). The limbic system, including the amygdala and hippocampus, processes emotions and memory.

The spinal cord transmits signals between the brain and body and coordinates reflexes. Thirty-one pairs of spinal nerves emerge from the cord. The peripheral nervous system includes the somatic division (voluntary control of skeletal muscles) and autonomic division (involuntary control of internal functions).

The autonomic nervous system has sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions. These systems work antagonistically to regulate heart rate, digestion, respiration, and other functions.

Neurological health concerns include traumatic brain injury, stroke, epilepsy, neurodegenerative diseases (Alzheimer's, Parkinson's), and mental health disorders. Brain health is supported by physical activity, cognitive stimulation, adequate sleep, social engagement, and management of cardiovascular risk factors.

The endocrine system regulates body functions through hormones secreted by glands into the bloodstream. Hormones are chemical messengers that bind to specific receptors on target cells, altering cellular activity.

The hypothalamus links the nervous and endocrine systems, controlling the pituitary gland. The pituitary gland (master gland) secretes hormones that regulate other endocrine glands and directly affect tissues. Anterior pituitary hormones include growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary releases oxytocin and antidiuretic hormone.

The thyroid gland regulates metabolism through thyroxine (T4) and triiodothyronine (T3). The parathyroid glands regulate calcium levels through parathyroid hormone. The adrenal glands produce cortisol (stress response, metabolism), aldosterone (fluid balance), and epinephrine and norepinephrine (fight-or-flight response).

The pancreas contains islets of Langerhans that produce insulin (lowers blood glucose) and glucagon (raises blood glucose). Diabetes mellitus results from insufficient insulin production (Type 1) or insulin resistance (Type 2). Type 2 diabetes is largely preventable through healthy weight, physical activity, and balanced nutrition.

The gonads (ovaries and testes) produce sex hormones that regulate reproductive function and secondary sex characteristics. Estrogen and progesterone are primary female hormones; testosterone is the primary male hormone.

Endocrine disruptors are environmental chemicals that interfere with hormone function. Sources include pesticides, plastics, and personal care products. Reducing exposure supports endocrine health.

The immune system defends against pathogens and foreign substances. Innate immunity provides immediate, nonspecific defense through physical barriers (skin, mucous membranes), chemical barriers (stomach acid, lysozyme), and cellular defenses (phagocytes, natural killer cells). Inflammation is an innate response that isolates pathogens and promotes healing.

Adaptive immunity develops in response to specific pathogens. B lymphocytes produce antibodies (humoral immunity). T lymphocytes directly attack infected cells (cell-mediated immunity). Memory cells provide long-lasting protection against previously encountered pathogens.

Active immunity results from exposure to pathogens (natural) or vaccines (artificial). Passive immunity involves receiving antibodies from another source, such as maternal antibodies or immunoglobulin injections, providing temporary protection.

Vaccines stimulate adaptive immunity without causing disease. They contain weakened or killed pathogens, pathogen components, or genetic material. Recommended immunization schedules protect against diseases including measles, mumps, rubella, polio, hepatitis, pertussis, tetanus, diphtheria, and influenza.

Immune dysfunction includes immunodeficiency (weakened response), autoimmunity (attacks self), and hypersensitivity (excessive response, allergies). HIV attacks helper T cells, progressively weakening immune function and leading to AIDS.

Immune health is supported by adequate sleep, balanced nutrition, regular physical activity, stress management, and avoiding tobacco and excessive alcohol.

The integumentary system (skin, hair, nails) protects against pathogens, UV radiation, and physical damage; regulates temperature; synthesizes vitamin D; and provides sensory information.

Skin has three layers. The epidermis is the outer layer containing keratinocytes, melanocytes (produce melanin for UV protection), and Langerhans cells (immune function). The dermis contains blood vessels, nerves, hair follicles, and glands. The hypodermis (subcutaneous layer) contains fat for insulation and energy storage.

Sweat glands regulate temperature through evaporative cooling. Sebaceous glands produce sebum that lubricates skin and hair. Hair provides insulation and protection. Nails protect digit tips and assist with manipulation.

Skin conditions include acne, eczema, psoriasis, and skin cancer. Melanoma is the most dangerous skin cancer, often resulting from UV exposure. Sun protection (limiting exposure, protective clothing, sunscreen) reduces skin cancer risk.

Wound healing involves hemostasis (bleeding control), inflammation, proliferation (new tissue formation), and remodeling. Proper wound care prevents infection and promotes healing.