Anatomy and Physiology

Anatomy and Physiology Defined

• Anatomy is the study of the body's structures and forms.
• Physiology is the study of how the body parts function.

Anatomy - Details of Form

• Microscopic anatomy involves structures not visible to the naked eye, including cytology and histology.
• Cytology studies body cells and their internal structure.
• Histology examines tissues.
• Gross anatomy (macroscopic anatomy) studies visible body parts and their relationships like intestines, stomach, brain, heart, and kidneys, comprising systemic, regional, surface, comparative, and embryology.
• Systemic anatomy focuses on the anatomy of each functional body system.
• Regional anatomy examines all structures within a specific body region as a complete unit.
• Surface anatomy examines both superficial anatomic markings and internal structures related to overlying skin.
• Comparative anatomy studies the similarities and differences across species.
• Embryology studies developmental changes from conception to birth.
• Specialized anatomy branches focus on medical diagnosis and research, including pathologic and radiographic anatomy.
• Pathologic anatomy studies anatomical changes resulting from diseases.
• Radiographic anatomy studies internal structure relationships via scanning procedures like ultrasound, MRI, or X-ray.

Physiology - Details of Function

• Physiology studies organ system functions, focusing on molecular and cellular levels, paralleling anatomy in breadth, and includes cardiovascular, neuro-, respiratory, reproductive, and pathophysiology.
• Cardiovascular physiology studies heart, blood vessels, and blood function.
• Respiratory physiology studies gas exchange between lungs and blood vessels.
• Reproductive physiology explores reproductive hormone regulation of reproductive cycles, sex cell production, and maturation.
• Pathophysiology studies the relationship between organ system function and disease or injury.

Integration of Anatomy and Physiology

• Anatomy (form) and physiology (function) are interrelated sciences.
• Anatomists need to understand function to appreciate form fully.
• Physiologists need to know form to understand body functions.

Levels of Organization

• Living organisms share properties like organization, metabolism, growth, development, responsiveness, regulation, and reproduction.
• Organization refers to the complex, hierarchical structure of the body.
• Metabolism is the sum of all bodily chemical reactions including anabolism and catabolism.
• Anabolism is a biochemical process where small molecules combine into larger ones.
• Catabolism is a process where large molecules break down into smaller ones.
• Growth is the physical enlargement of an organism.
• Development (differentiation) is when cells become specialized for specific functions, such as nerve cells.
• Responsiveness is the ability to sense and react to stimuli.
• Regulation is maintaining a stable internal environment (homeostasis).
• Reproduction is creating new cells for growth, maintenance, and repair.
• Sex cells develop a new organism.
• Organization levels in humans increase in complexity from chemical, cellular, tissue, organ, organ system, to organism level.
• The chemical level involves atoms (smallest units) and molecules (combinations of atoms).
• The cellular level consists of cells, which are the basic functional and structural units.
• Biochemical macromolecules (carbohydrates, lipids, proteins, nucleic acids) and organelles interface the chemical and cellular levels.
• Tissue level involves groups of similar cells with common functions and embryonic origins.
• The organ level is composed of two or more tissue types performing complex functions.
• The organ system level contains organs working together for a common function.
• The organism level is the highest level, with all organ systems integrated functionally.

Organ Systems Introduction

• Complex organisms perform many complex metabolic processes.
• These complex processes require specialized division of physiological labor with each organ system assigned a major physiological task.
• Organ systems multi-task, performing more than just the main task they are named for.
• Some tasks are shared among organ systems, such as acid/base balance being controlled by both the respiratory and renal systems.
• Some organs are part of multiple organ systems due to their primary and secondary tasks.

Language of Anatomy & Anatomic Position

• Precise anatomical language allows clinicians and researchers to discuss features and functions clearly.
• Anatomic position has the body erect, limbs at sides, palms anterior, feet together at a 45-degree angle.

Sections and Planes

• A section is an actual cut or slice exposing internal anatomy.
• A plane is an imaginary flat surface through the body, including coronal, transverse, sagittal, and oblique.
• The coronal (frontal) plane is a vertical plane dividing the body into anterior (front) and posterior (back) parts.
• The transverse (horizontal) plane divides the body into superior (top) and inferior (bottom) parts.
• The sagittal plane divides the body into right and left halves.
• A midsagittal plane is a cut down the midline creating equal halves, while a sagittal plane creates unequal halves.
• Coronal, transverse, and sagittal planes are at 90-degree angles to each other, while oblique planes are at other angles.

Anatomic Directions

• Relative directional terms are used after positioning the body in the anatomical position.
• Anterior means toward the front surface.
• Posterior means toward the back surface.
• Dorsal is the back side of the human body.
• Ventral is the belly side of the human body.
• Proximal is nearest to the point of attachment on appendages.
• Distal is farthest from the point of attachment on appendages.

Regional Anatomy

• The human body is divided into axial and appendicular regions.
• The axial region includes the head, neck, and trunk.
• The appendicular region comprises the upper and lower limbs.

Body Cavities and Membranes

• Internal organs/systems reside in enclosed cavities named after surrounding bones or organs.
• The main cavities are posterior and ventral, further divided into smaller cavities.
• The posterior cavity has cavities encased in bone, physically and developmentally different from the ventral cavity.
• It has two subdivisions: cranial and vertebral.
• The cranial cavity (endocranium) is formed by the cranium bones.
• The vertebral cavity houses the spinal cord, formed by the vertebral column bones.
• The ventral cavity contains the thoracic and abdominopelvic cavities.
• Ventral cavities are lined by serous membranes, unlike posterior cavities.
• A serous membrane is a continuous cell layer (compared to the single plasma membrane).
• Serous membranes have parietal (lining body walls) and visceral (covering organ surfaces) layers.
• Between layers is the serous cavity, a potential space.
• Serous membranes secrete oily serous fluid, a lubricant preventing friction among organs.
• The thoracic cavity has mediastinum, pericardial, and pleural cavities.
• The mediastinum cavity is in the thoracic cavity's median space, containing the heart, thymus, esophagus, trachea, and major blood vessels.
• The pericardial cavity, within the mediastinum, encloses the heart in the pericardium, a two-layered serous membrane consisting of:
  • parietal pericardium (outermost layer) and visceral pericardium (heart’s external surface).
• The pericardial cavity is the potential space between the parietal and visceral pericardium.
• The pleural cavities surround lungs on the thoracic cavity's right and left, consisting of parietal (outer) and visceral (inner) layers.
• he abdominopelvic cavity, a ventral cavity subdivision, separates from the thoracic cavity, with diaphragm muscle.
• The abdominopelvic cavity divides into abdominal and pelvic cavities at the superior aspects of the hip bones.
• The abdominal cavity lies superior (above hip bones) and contains digestive organs, kidneys, and ureters.
• The pelvic cavity lies inferior (below hip bones) and contains the large intestine, ureter, bladder, and reproductive organs.
• Similar to pleural/pericardial membranes, the peritoneum forms a serous membrane lining the abdominopelvic cavity with parietal and visceral layers.
• Parietal peritoneum is the abdominopelvic cavity's outer lining.
• The visceral peritoneum covers abdominopelvic organ surfaces.
• The peritoneal cavity is the potential space between membranes containing serous fluid.

Abdominopelvic Regions and Quadrants

• Anatomists and clinicians divide the abdominopelvic cavity into smaller compartments including nine-compartment and quadrant methods.
• The nine-compartment method includes umbilical, epigastric, hypogastric, right/left hypochondriac, right/left lumbar, and right/left iliac regions.
• Healthcare professionals divide the abdomen into four quadrants using imaginary transverse and midsagittal planes through the umbilicus.
• These quadrants are right upper, right lower, left upper, and left lower.

Homeostasis

• Homeostasis keeps a stable internal environment despite changes.
• Homeostatic control systems maintain homeostasis: receptor, control center, effector.
• The receptor detects changes in a regulated variable (substance or process).
• Stimulus is the change in a variable.
• The control center interprets the input from the receptor and uses the effector to initiate changes.
• The effector changes the stimulus to bring the variable back to its optimal, homeostatic range.
• These homeostatic system components form a dynamic control feedback loop.
• The feedback loop has:
  • a receptor receiving a stimulus
  • transmitting information to the control center
  • the control center integrates input and directs a change via effectors
  • the effectors receive input from the control unit to return the body to homeostasis.
• Homeostatic control systems adjust variables within a normal range or amplify the stimulus.
• Negative feedback opposes the stimulus.
• Positive feedback reinforces the stimulus in the same direction.

Negative Feedback

• Negative feedback controls most body processes by opposing the stimulus to maintain a set point.
• Temperature regulation exemplifies negative feedback.
• Temperature receptors in skin and blood monitor human body temperature by passing through the hypothalamus.
• Skin temperature receptors signal the hypothalamus, the body's temperature control unit.
• The hypothalamus signals thermal effectors (skin blood vessels, sweat glands, skeletal muscles, and hair follicle smooth muscles).
• In a cold environment:
  • surface blood vessels decrease lumen diameter reducing blood flow and heat loss
  • skeletal muscles shiver
  • smooth muscle contracts causing goosebumps.
• Hot environments do the opposite which causes:
  • skin blood vessels increase lumen diameter
  • skeletal muscles decrease motion
  • sweat glands produce sweat.

Positive Feedback

• Positive feedback reinforces the stimulus until a climatic event allows the body to return to homeostasis.
• Breast-feeding is a homeostasis example of positive feedback.
• The baby's suckling is an initial stimulus detected by nipple receptors, which signal the hypothalamus.
• A signal from the hypothalamus goes to the anterior pituitary gland, where oxytocin is secreted.
• Oxytocin travels to mammary glands (effectors), causing milk secretion.
• Suckling force controls milk secretion; the stimulus intensifies the response.
• Once the baby stops suckling, the cycle stops which removes the initial response.
• Blood coagulation and labor contractions are other homeostasis examples of positive feedback.

Homeostatic Imbalance & Disease

• Disease occurs when homeostasis cannot maintain a stable internal environment.
• Homeostatic imbalance may occur due to normal aging.
• Normal homeostatic ranges may change with aging.
• Diagnosis finds the specific cause of the homeostatic imbalance to then treat a patient.
• Drugs can induce homeostatic imbalance to treat disease, such as SSRIs raising serotonin levels to treat depression.
• Medications can cause side effects that alter body processes and chemical levels.

Medical Imaging

• Radiography is mainly used to get a diagnostic image of a body part.
• Sonography (ultrasound) sends high-frequency ultrasonic waves into the body, receives reflections, and forms an image of internal organs.
• Computerized Tomography (CT scan ) is a sophisticated X-ray application, creating multiple axial images of body regions and analyzed by a computer to produce a 3D image.
• Digital Subtraction Angiography is a modified 3D X-ray technique used to view blood vessels.
• Dynamic Spatial Reconstruction is a unique radiologic method that provides 3D images as they move.
• Magnetic Resonance Imaging (MRI) provides non-invasive soft tissue images using magnetic fields/radio waves to alter hydrogen atoms in cells.
• More water in soft tissues means the MRI visualizes them better than hard tissues, like bone.
• Positive Emission Tomography (PET scan) uses radioactivity-labeled glucose to analyze tissue metabolism, determining which are metabolically active.

Anatomy is the study of the body's structures, while physiology studies the function of body parts. Microscopic anatomy examines structures not visible to the naked eye, like cells and tissues. Gross anatomy studies visible body parts and their relationships.