The Healthy Body: Anatomy and Physiology

The Healthy Body

• Anatomy studies the structure of body parts and their relationships.
  • Gross/Macroscopic Anatomy examines large body structures visible to the naked eye, like heart, lungs, and kidneys.
  • Microscopic Anatomy studies structures too small for naked eye observation.
• Physiology concerns the function of the body and how body parts work to sustain life.

Levels of Structural Organization

• Chemical Level: atoms combine to form molecules, which then form organelles.

• Cellular Level: molecules combine to form cells, varying in size and shape to reflect unique functions.

• Tissue Level: similar cells group together for a common function forming tissues, including epithelial, muscle, connective, and nervous tissues.

  • Epithelial Tissue covers body surfaces and lines cavities.
  • Muscle Tissue facilitates movement.
  • Connective Tissue supports and protects body organs.
  • Nervous Tissue provides rapid internal communication via electrical impulses.

• Organ Level: complex functions become possible, such as the stomach's epithelium lining producing digestive juices, muscle walls churning contents, connective tissue reinforcing walls, and nerve fibres stimulating digestive activity.

• Organ System Level: organs work together for a common purpose, such as the cardiovascular system's heart and blood vessels circulating blood.

• Organismal Level: all structural levels work together to sustain life.

The Body's Organ Systems

• Integumentary System: forms external body covering, protects tissues from injury, synthesizes vitamin D, and houses receptors and glands.
• Skeletal System: protects and supports organs, provides muscle framework for movement, forms blood cells, and stores minerals.
• Muscular System: allows manipulation, locomotion, and facial expression, maintains posture, and produces heat.
• Nervous System: acts as a fast-acting control system, responding to internal and external changes.
• Endocrine System: glands secrete hormones regulating processes like growth and reproduction.
• Cardiovascular System: transports blood carrying oxygen, carbon dioxide, nutrients, and wastes.
• Lymphatic System/Immunity: picks up leaked fluid, disposes of debris, and houses lymphocytes for immunity.
• Respiratory System: supplies oxygen and removes carbon dioxide through gas exchange in the lungs.
• Digestive System: breaks down food into absorbable units distributed to body cells; indigestible waste is eliminated as feces.
• Urinary System: eliminates nitrogenous wastes and regulates water, electrolyte, and acid-base balance.
• Male Reproductive System: produces sperm and male sex hormone, aiding sperm delivery.
• Female Reproductive System: produces eggs and female sex hormones; serves as fertilization and foetal development site; mammary glands produce milk.

Necessary Life Functions

• Movement: activities promoted by the muscular system, including propelling oneself and manipulating the environment; also involves internal movement of substances like blood, food, and urine, including contractility: it enables the movement muscle cells by shortening.
• Responsiveness/Excitability: ability to sense and respond to environmental changes, with the nervous system playing a key role due to highly excitable nerve cells like a withdrawal reflex from touching broken glass.
• Digestion: ingested food is broken down into simple molecules for absorption into the blood and distribution to body cells, with the digestive system in multicellular organisms performing these functions.
• Metabolism: it includes all chemical reactions within body cells, breaking down substances (catabolism), synthesizing complex substances (anabolism), and using nutrients and oxygen to produce ATP via cellular respiration, dependent on the digestive and respiratory systems to make nutrients and oxygen available and the cardiovascular system for distribution.
• Excretion: removal of wastes from the body, with the digestive system removing indigestible food residues and the urinary system disposing of nitrogenous metabolic wastes like urea.
• Reproduction: occurs at the cellular level involving the cellular reproduction of identical daughter cells for growth or repair, and at the organismal level involving a whole new person
• Growth: an increase in size of a body part or the organism, primarily accomplished by increasing cell numbers.

Survival Needs

• Nutrients: taken in via the diet, these contain the chemical substances used for energy and cell building where plant-derived foods are rich in carbohydrates, vitamins, and minerals, while animal foods are richer in proteins and fats; carbohydrates, proteins and fats
  • Proteins: essential the building of the cell structure
  • Minerals & Vitamins: required for chemical reactions in oxygen transport in the blood
  • Example(calcium): helps make bones hard and is required for blood clotting.
• Oxygen: gas needed in the world; cells can survive only a few minutes without it, and accounts for approximately 20% of the air; which Respiratory and cardiovascular systems make oxygen available to blood/ cells.
• Water: accounts for 50-60% of body weight, providing a necessary environment for chemical reactions and forming the fluid base for body secretions and excretions.
• Normal body temperature: maintained to sustain life; metabolic reactions slow down below 37°C, and the muscular system activity generates most body heat.
• Atmospheric pressure: the force that air exerts on the surface of the body, on which breathing and gas exchange in the lungs depend.

Directional Terms

• Anatomical position includes an erect body with feet slightly apart, palms facing forward, and thumbs pointing away.
• Axial part includes the head, neck, and trunk.
• Appendicular part consists of the limbs.
• Sagittal plane: a vertical plane dividing the body vertically .
  • Median plane (midsagittal plane): a sagittal plane in the midline
  • Parasagittal planes: all other sagittal planes that are offset from the midline
• Frontal planes: divide the body into anterior and posterior parts and referred to as coronal plane.
• Transverse plane: it runs horizontally: dividing the body into superior and inferior and referred to as "cross section".
• Oblique sections: are cuts made diagonally between the horizontal and vertical planes.

Body Cavities

• Dorsal body cavity: protects the nervous system that has two subdivisions.
  • Cranial cavity in the the skull, where it encases the brain.
• Vertebral/spinal cavity runs within bony vertebral column enclosing the spinal cord.
  • Both brain and spinal cord membranes covered with meninges
• Ventral body cavity: larger anterior body that is subdivided into two sections.
  • Thoracic cavity: ribs and muscles of the chest.
  • It subdivides further into Plural cavities: enveloping lung and mediastinum: it encloses the pericardial cavity which the organs in the cavity
  • Abdominopevic cavity: divided to. the largest subdividing cavity
  • Abdominal cavity: includes stomach, intestines, spleen and liver.
  • Pelvic cavity: urinary bladder, reproductive organs and rectum.
• Serous membrane (Serosa): a type of smooth tissue that lines the walls and contents of all cavities. Serous membrane that contains (Parietal Peritoneum) or (Reteroperitoneal organs- Kidneys or Pancreas). Membranes that contain visceral layer that cover organs separated with serous fluid that is secreted.

Homeostasis

• Homeostasis: the ability to maintain relatively stable internal conditions despite continuous changes; dynamic equilibrium: internal conditions vary but stay in relatively narrow limits; feedback is activated systems for when the body leaves.
• Three main homeostatic control: receptor: monitors the environment and sends stimuli: a sensor that monitors the environment; stimulus causes changes to the control center and responds back along afferent
  • Control center: decides set point and responds to level.
  • Afferent (approaches that signals the center).
  • Efferent (to exit through response system)
  • Effector: effects stimuli.
• Most homeostatic system: Negative feedback to turn off original stimuli; Examples are blood pressure and sugar level. Positive feedback: Original response increases stimuli. Examples: childbirth, breastfeeding and clood clotting; examples of regulation include body temperature regulation or negative feedback; control center: hypothalamus, and elevated body temperature.