THE HUMAN BODY AN ORIENTATION An Overview of Anatomy and Physiology

Anatomy Study of the structure of body parts and their relationships to each other Anatomy: Greek meaning to cut apart

Physiology Study of the function of body parts How all the body parts work and carry out their life-sustaining activities

Topics of Anatomy Gross (macroscopic) anatomy: the study of structures large enough to be seen with the naked eye Regional anatomy: all the body structures (muscles, bones, blood vessels, nerves, etc.) in a given body region , such as the abdomen or leg, are examined at the same time Systemic anatomy: body is studied system by system Example: when studying the cardiovascular system, you would examine the heart and the blood vessels of the entire body Surface anatomy: internal body structures as they relate to the overlying skin Used when identifying the bulging muscles beneath a bodybuilder’s skin, and clinicians use it to locate appropriate blood vessels in which to feel pulses and draw blood

Topics of Anatomy Microscopic anatomy: the study of structures that are too small to be seen with the naked eye Cytology: study of individual cells Histology: study of tissues Developmental anatomy: the study of the change in body structures over the course of a lifetime Embryology: concerns developmental changes that occur before birth

Topics of Anatomy Specialized Branches of Anatomy Pathological anatomy: study of structural changes associated with disease Radiographic anatomy: study of internal structures using specialized visualization techniques (X-rays or special scanning devices) Molecular biology: study of biological molecules

Topics of Physiology Considers the function of specific organ systems: Examples: Renal physiology: concerns kidney function and urine production Neurophysiology: explains the workings of the nervous system Cardiovascular physiology: examines the operation of the heart and blood vessels While anatomy provides us with a static image of the body’s architecture, physiology reveals the body’s dynamic nature

Topics of Physiology Focuses on cellular and molecular events: Individual cells and the chemical reactions that go on within them Principles of physics which helps to explain electrical currents, blood pressure, and the way muscles use bones to cause body movements

Complementarity of Structure and Function Function is dependent on structure, and the form of a structure relates to its function: What a structure can do depends on its specific form Examples: Bones can support body organs because they contain hard mineral deposits Blood flows in one direction through the heart because the heart has valves that prevent backflow Lungs can serve as a site for gas exchange because the walls of their air sacs are extremely thin

Levels of Structural Organization (1):Chemical level is the simplest level of organization: Atoms, tiny building blocks of matter, combine to form molecules such as water and proteins Molecules combine in specific ways to form organelles, which are the basic unit of living cells Cells are the smallest units of living things All cells have some common functions, but individual cells vary widely in size and shape, reflecting their unique functions in the body

Levels of Structural Organization (2):Cellular level: smallest unit of life, and varies widely in size and shape according to the cell’s function (3):Tissue level: groups of similar cells having a common function Four basic tissue types: each tissue type has a characteristic role in the body Epithelium: covers the body surface and lines its cavities Muscle: provides movement Connective: supports and protects body organs Nervous: provides a means of rapid internal communication by transmitting electrical impulses

Levels of Structural Organization (4):Organ level: made up of discrete structures that are composed of a least two groups of tissues that work together to perform a specific function in the body Stomach: epithelium lining, muscles, blood vessels, connective tissues, nerve fibers, etc. (5):Organ system level: a group of organs that work closely together to accomplish a specific purpose Respiratory and circulatory system, digestive and circulatory systems (6):Organismal level: the total of all structures working together to promote life The living human being

Levels of Structural Organization

Maintaining Life Necessary Life Functions (a): Maintaining Boundaries: allows an organism to maintain separate internal and external environments, or separate internal chemical environments Integumantary System or Skin (b): Movement: allows the organism to travel through the environment, and allows transport of molecules within the organism Skeletal, Circulatory, Muscular Systems (c): Responsiveness: or irritability, is the ability to detect changes in the internal or external environment and respond to them Muscular System

ORGAN SYSTEMS

Maintaining Life Necessary Life Functions (d): Nervous System: Responsiveness to external and internal environments by activating muscles and glands (e): Endocrine System: Regulating body functions such as: growth, reproduction, and nutrition (f): Cardiovascular System: Transportation of nutrients, waste, gases, and hormones throughout the body

ORGAN SYSTEMS

Maintaining Life Necessary Life Functions (g): Lymphatic System/Immunity: Body defenses (h): Respiratory System: External and internal gas exchanges (i): Digestive System: Breakdown and absorption of nutrients

ORGAN SYSTEMS

Maintaining Life Necessary Life Functions (j): Urinary System: Absorption of waste from the blood and elimination (k): Male Reproductive System: Production of sperm (l): Female reproductive System: Production of eggs

ORGAN SYSTEMS

Maintaining Life Necessary Life Functions Digestion is the process of breaking down food into molecules that are usable by the body Metabolism includes all chemical reactions that occur in the body Excretion is the process of removing wastes Reproduction is the process of producing more cells or organisms Growth is an increase in size in body parts or the whole organism

Examples of selected interrelationships among body organ systems Integumentary system protects the body as a whole from the external environment Digestive and respiratory systems, in contact with the external environment, take in nutrients and oxygen, respectively, which are then distributed by the blood to all body cells Elimination of metabolic wastes is accomplished by the urinary and respiratory systems

ORGAN SYSTEMS

Survival Needs The ultimate goal of all body systems is to maintain life Life is extraordinarily fragile and requires that several factors be present: These factors are called survival needs and include: Nutrients: consumed chemical substances that are used for energy and cell building Oxygen: required by the chemical reactions that release energy from foods Water: most abundant chemical substance in the body, provides an environment for chemical reactions and a fluid for secretions and excretions Normal body temperature: required for the chemical reactions of the body to occur at the proper rate Atmospheric pressure: must be within an appropriate range so that proper gas exchange occurs in the lungs

Homeostasis The ability of the body to maintain a relatively constant internal environment, regardless of environmental changes: Body temperature Blood pH

Homeostatic Control Mechanisms Communication within the body is essential for homeostasis Accomplished chiefly by the nervous and endocrine systems All homeostatic control mechanisms have at least three interdependent components: 1. Receptor: type of sensor that monitors the environment and responds to changes, called stimuli, by sending information (input) to the second component (control center)

Homeostatic Control Mechanisms 2. Control Center: Information flows from the receptor to the control center along the afferent pathway Structure that determines the set point (level or range at which a variable is to be maintained) for a variable, analyzes input, and coordinates an appropriate response Variable: the regulated factor or event

Homeostatic Control Mechanisms 3. Effector: Provides the means for the control center’s response (output) to the stimulus Structure that carries out the response directed by the control center Information flows from the control center to the effector along the efferent pathway The results of the response then feed back to influence the stimulus, either depressing it (negative feedback) so that the whole control mechanism is shut off or enhancing it (positive feedback) so that the reaction continues at an even faster rate

CONTROL SYSTEM

Negative Feedback Mechanisms Most homeostatic control mechanisms are negative feedback mechanisms In these systems, the output shuts off the original stimulus or reduces its intensity These mechanism cause the variable to change in a direction opposite to that of the initial change, returning it to its “ideal” value Both the nervous system and the endocrine system are important to the maintenance of homeostasis The goal of negative feedback mechanisms is to prevent sudden, severe changes in the body

Negative Feedback Mechanisms Home heating system connected to a temperature-sensing thermostat Thermostat houses BOTH the receptor and the control center If thermostat is set at 20oC (68oF), the heating system (effector) is triggered ON when the house temperature drops below that setting As the furnace produces heat and warms the air, the temperature rises, and when it reaches 20oC or slightly higher, the thermostat triggers the furnace OFF This process results in a cycling of “furnace-ON” and “furnace-OFF” so that the temperature in the house stays very near the desired temperature of 20oC Your body thermostat, located in a part of your brain called the hypothalamus, operates in a similar fashion

Negative Feedback Mechanisms To carry out normal metabolism, body cells need a continuous supply of glucose, their major fuel for producing cellular energy, or ATP Blood sugar levels are normally maintained around 90 milligrams (mg) of glucose per 100 millimeters (ml) of blood Rising glucose levels stimulate the insulin-producing cells of the pancreas, which respond by secreting insulin into the blood Insulin accelerates the uptake of glucose by most body cells It also encourages storage of excess glucose as glycogen in the liver and muscles Consequently, blood sugar levels ebb back toward the normal set point, and the stimulus for insulin release diminishes

NEGATIVE FEEDBACK

Negative Feedback Mechanisms Glucagon, another pancreatic hormone, has the opposite effect of insulin Its release is triggered as blood sugar levels decline below the set point Glucagon secretion is stimulated Glucagon targets the liver, causing it to release its glucose reserves from glycogen into the blood Consequently, blood sugar levels increase back into the homeostatic range There are hundreds of Negative Feedback Mechanisms (regulation of heart rate, blood pressure, rate and depth of breathing, and blood levels of oxygen, carbon dioxide, and minerals)

NEGATIVE FEEDBACK

Positive Feedback Mechanisms Result or response enhances the original stimulus so that the activity (output) is accelerated A positive feedback mechanism causes the variable to change in the same direction as the original change, resulting in a greater deviation from the set point Positive feedback mechanisms typically activate events that are self-perpetuating Once initiated, have an amplifying effect Most positive feedback mechanisms are not related to the maintenance of homeostasis Homeostatic imbalance often results in disease

Positive Feedback Mechanisms Examples: Enhancement of labor contractions during birth: Oxytocin, a hypothalamic hormone, intensifies labor contractions during the birth of a baby Causes the contractions to become more frequent and more powerful until the baby is finally born, an event that ends the stimulus for oxytocin release and shuts off the positive feedback mechanism

Positive Feedback Mechanisms Examples: Blood clotting: Blood clotting is a normal response to a break in the lining of a blood vessel 1. Once vessel damaged has occurred 2. Blood elements called platelets immediately begin to cling to the injured site 3. Platelets release chemical that attract more platelets 4. This rapidly growing pileup of platelets initiates the sequence of events that finally forms a clot

POSITIVE FEEDBACK

Homeostatic Imbalance Homeostasis is so important that most disease is regarded as a result of its disturbance, a condition called Homeostatic Imbalance Causes: As we age, our body’s control systems become less efficient Negative feedback mechanisms become overwhelmed and destructive positive feedback mechanisms take over

Language of Anatomy Anatomical Position and Directional Terms To describe body parts and position accurately, we need an initial reference point and must indicate direction The anatomical reference point is a standard body position called the Anatomical Position Anatomical Position: position in which the body is: Erect with feet only slightly apart Palms face forward Thumbs point away from the body

REGION TERMS

REGION TERMS

Language of Anatomy Anatomical Position and Directional Terms In anatomical position, right and left refer to the right and left sides of the person viewed—NOT those of the observer In anatomy, anatomical position is always assumed, regardless of the actual position of the body

Language of Anatomy Anatomical Position and Directional Terms Directional terms are used to explain exactly where one body part is in relation to another Example: The ears are located on each side of the head to the right and left of the nose Using anatomical terminology, this condenses to,: The ears are lateral to the nose Saves words and is less ambiguous Anatomical meanings are VERY PRECISE

Orientation and Directional Terms

Orientation and Directional Terms

Orientation and Directional Terms

Regional Terms There are two fundamental divisions of the body: Axial region: Makes up the main axis of our body Includes the head, neck, and trunk Appendicular region: Consists of the appendages, or limbs Attached to the body’s axis Consists of the upper and lower limbs Regional terms are used to designate specific areas within the major body divisions The common term for each of these body regions is provided (in parentheses)

REGION TERMS

REGION TERMS

Body Planes and Sections For anatomical studies, the body is often sectioned (cut) along a flat surface called a plane Body planes are flat surfaces that lie at right angles to each other Sagittal plane: a vertical plane that separates the body into right and left parts Median, or midsagittal plane: lies exactly along the body’s midline Parasagittal plane (para=near): lies offset from the midline Frontal plane: a vertical plane that separates the body into anterior and posterior parts Transverse, or horizontal, plane: a plane that runs horizontally from right to left, and divides the body into superior and inferior parts

BODY PLANES

Body Planes and Sections Transverse, or horizontal, plane: a plane that runs horizontally from right to left, and divides the body into superior and inferior parts Many different transverse planes exist, at every possible level from head to foot Transverse section, or cross section, is a cut made along the transverse plane Oblique sections are cuts made at angles between the horizontal and vertical planes The ability to interpret sections made through the body, especially transverse sections, is important in the clinical sciences New medical imaging devices produce sectional images rather than three-dimensional images

BODY PLANES

Body Cavities and Membranes Within the axial portion of the body are two large cavities called the dorsal and ventral body cavities Body cavities are spaces within the body that are closed to the outside and contain the internal organs

BODY CAVITIES

BODY CAVITIES

Dorsal Body Cavity The space that houses the central nervous system, and has two subdivisions: the cranial cavity and the vertebral cavity Cranial cavity is within the skull, and encases the brain Vertebral, or spinal, cavity is within the vertebral column, and encloses the spinal cord

BODY CAVITIES

BODY CAVITIES

Ventral Body Cavity Is anterior to and larger than the dorsal cavity and has two main subdivisions: the thoracic cavity, and the abdominopelvic cavity Houses the body organs collectively called the viscera (viscus=an organ in a body cavity), or visceral organs Thoracic cavity: Is a superior division of the ventral cavity that is further subdivided into the lateral pleural cavities that surround the lungs Thoracic cavity also contains the medulla mediastinum, which includes the pericardial cavity surrounding the heart and the space surrounding the other thoracic structures (esophagus, trachea, and others) Diaphragm Muscle separates the Thoracic and Abdominopelvic Regions Abdominopelvic Regions and Quadrants: Inferior to the Thoracic Cavity There are nine abdominopelvic regions used primarily by anatomists There are four quadrants used primarily by medical personnel

BODY CAVITIES

BODY CAVITIES

Membranes in the Ventral Body Cavity The walls of the ventral body cavity and the outer surfaces of the organs it contains are covered by a thin, double-layered membrane, the serosa, or serous membrane Serous membranes, or serosae, cover the inner walls of the ventral cavity and the outer surfaces of organs Serous membranes secrete and are separated by a thin layer of lubrication fluid called serous fluid, which allows organs to slide without friction along cavity walls and between each other Parietal serosa lines the body cavity walls, and is named for the specific cavities it is associated with Visceral serosa covers the outer surfaces of organs, and is named for the specific organs it is associated with Parietal pericardium lines the pericardial cavity Visceral pericardium covers the heart within that cavity Parietal pleura lines the walls of the thoracic cavity Visceral pleura covers the lungs Parietal peritoneum is associated with the walls of the abdominalpelvic cavity Visceral peritoneum covers most of the organs within that cavity

SEROUS MEMBRANE Parietal pericardium lines the pericardial cavity Visceral pericardium covers the heart within that cavity

SEROUS MEMBRANE

Membranes in the Ventral Body Cavity You can visualize the relationship between the serosal layers by pushing your fist into a limp balloon The part of the balloon that clings to your fist can be compared to the visceral serosa clinging to the organ’s external surface The outer wall of the balloon then represents the parietal serosa that lines the walls of the cavity

SEROUS MEMBRANE

Homeostatic Imbalance When serous membranes are inflamed, they typically produce less lubricating serous fluid This leads to excruciating pain as the organs stick together and drag across one another, as anyone who has experienced pleurisy (inflammation of the pleurae: thoracic cavity) or peritonitis (inflammation of the peritoneal: abdominal cavity)

Abdominopelvic Regions Because the abdominopelvic cavity is large and contains several organs, it helps to divide it into smaller areas for study Cavity divided into 9 regions Umbilical region: centermost region deep to and surrounding the umbilicus (navel) Epigastric region: located superior to the umbilical region (epi=upon, above; gastri=belly) Hypogastric (pubic) region: located inferior to the umbilical region (hypo=below)

ABDOMINAL REGION

ABDOMINAL REGIONS

Abdominopelvic Regions Right and left iliac, or inguinal regions: located lateral to the hypogastric region (iliac=superior part of the hip bone)(inguinal=groin: between thigh and trunk) Right and left lumbar regions: lie lateral to the umbilical region (lumbus=loin: between ribs and pelvis) Right and left hypochondriac regions: flank the epigastric region laterally (chondro=cartilage)

ABDOMINAL REGION

ABDOMINAL REGIONS

Quadrants Medical personnel usually use a simpler scheme to localize the abdominopelvic cavity organs In this scheme, one transverse and one median sagittal plane pass through the umbilicus at right angles The resulting quadrants are named according to their positions from the subject’s point of view: Right upper quadrant (RUQ) Left upper quadrant (LUQ) Right lower quadrant (RLQ) Left lower quadrant (LLQ)

ABDOMINAL REGION

Other Body Cavities Oral and digestive cavities are continuous cavities that extend from the mouth through the digestive system to the anus Nasal cavity is within and posterior to the nose Part of the respiratory system Orbital cavities (orbits) in the skull house the eyes Middle ear cavities are within the skull just medial to the eardrums, and house the bones that transmit sound vibrations to the inner ears Synovial cavities are joint cavities Enclosed within fibrous capsules that surround movable joints (elbow and knee) Lined with a lubricating fluid-secreting membranes Secrete a lubricating fluid that reduces friction as the bones move across one another

OTHER CAVITIES

Medical Imaging X-ray (radiograph) CAT: Ccomputerized axial tomography Xenon CT DSR: Dynamic spatial reconstruction DSA: Digital subtraction angiography PET: Positron emission tomography Sonography (ultrasound imaging) MRI: Magnetic resonance imaging MRS: Magnetic resonance spectroscopy

IMAGING