Chapter 1: The Human OrganismTuesday, November 16, 201010:05 PM IntroductionHuman anatomy and Physiology - study of the structure and function of the human body Anatomy and PhysiologyAnatomy - scientific discipline that investigates the structure of the body

- means to disect, or cut apart and separate, the parts of the body for study- covers a wide range of studies- examines the relationship between the structure of a body part and its function

Two basic approaches to the study of anatomy:1. Systematic Anatomy - the study of the body by systems2. Regional Anatomy - the study of the organization of the body by areas

Surface anatomy and anatomical imaging are used to examine the internal structures of a living person. Both provide important information useful in diagnosing disease.Surface Anatomy - the study of external featuresAnatomical Imaging - involves the use of x-rays, ultrasound, magnetic resonance imaging (MRI), and other technologies to create pictures of internal structuresAnatomical Anomalies - structures that are unusual and different from the normal patternPhysiology - scientific discipline that deals with the processes or functions of living things

- important to recognize structures as dynamic rather than static, or unchangingMajor goals of Physiology:

1. Understand and predict the body`s responses to stimuli2. Understand how the body maintains conditions within a narrow range of values in the presence of a continually changing environment

Physiology is divided according to:1. The organisms involved2. The levels of organization within a given organism

Human physiology is the study of a specific organism, the human, whereas cellular physiology and systemic physiology are examples of physiology that emphasize specific organizational levels. Structural and Functional OrganizationChemical LevelInvolves interaction between atoms, which are tiny building blocks of matterCell LevelCells - basic structural and functional units of organismsOrganelles - small structures that make up cellsTissue LevelTissue - group of similar cells and the materials surrounding themClassified into four primary tissue types: epithelial, connective, muscle, and nervousOrgan LevelOrgan - composed of two ore more tissue types that together perform one or more common functionsOrgan System LevelOrgan System - group of organs classified as a unit because of a common function or set of functionsCoordinated activity of the organ systems is necessary for normal functionOrganism LevelOrganism - any living thing considered as a whole

Human organism is a complex of organ systems that are mutually dependent on one another Characteristics of Life1. Organization - condition in which the parts of an organism have specific relationships to each other and the parts interact to perform specific functions2. Metabolism - sum of the chemical and physical changes taking place in an organism3. Responsiveness - ability of an organism to sense changes in its external or internal environment and make the adjustments that help maintain its life4. Growth - results in an increase in size of all or part of the organism5. Development - includes the changes an organism undergoes through time; usually involves growth, but it also involves differentiationDifferentiation - change in cell structure and function from generalized to specialized6. Reproduction - formation of new cells or new organisms HomeostasisHomeostasis - existence and maintenance of a relatively constant environment within the bodyNormal cell functions depend on the maintenance of the cell`s fluid environment within a narrow range of conditionsConditions are called variablesVariables - values can changeSet Point - ideal normal valueNormal Range of Values - increases and decreases slightly around the set pointOrgan systems help control the body`s internal environment so that it remains relatively constantHomeostasis is the maintenance of a normal range of values but this does not mean that all variables are maintained within the same narrow range of values at all timesPurpose of medical therapy is to overcome illness by assisting negative-feedback mechanismsNegative FeedbackMost systems of the body are regulated by negative-feedback mechanisms, which maintain homeostasisNegative - any deviation from the set point is made smaller or is resistedDoes not prevent variation but maintains variation within a normal rangeMany negative-feedback mechanisms have three components:

1. Receptor - monitors the value of a variable2. Control Center - receives information about the variable from the receptor, establishes the set point, and controls the effector3. Effector - produces responses that change the value of the variable

Example: maintenance of normal blood pressureCase Study: Orthostatic Hypotension

Orthostasis - literally means "to stand"Hypotension - refers to low blood pressureOrthostatic Hypotension - significant drop in blood pressure on standing; when a person changes position from lying down to standing, blood "pools" within the veins below the heart because of gravity, and less blood returns to the heart; consequently, blood pressure decreases because the heart has less blood to pump

Positive FeedbackPositive-feedback mechanisms - not homeostatic and are rare in healthy individualsPositive - when a deviation from a normal value occurs, the response of the system is to make the deviation even greaterUsually creates a cycle leading away from homeostasis and in some cases results in deathExample: inadequate delivery of blood to cardiac (heart) muscle

Example of a normally occurring positive-feedback mechanism: birth Terminology and the Body PlanEtymology - origin of new words; most are derived from Greek or LatinWords are often modified by adding a prefix or suffixBody PositionsAnatomical Position - refers to a person standing erect with the face directed forward, the upper limbs hanging to the sides, and the palms of the hands facing forwardSupine - lying face upwardProne - lying face downwardPosition of the body can affect the description of body parts relative to each otherTo avoid confusion, relational descriptions are always based on the anatomical position, no matter the actual position of the bodyDirectional TermsDescribe parts of the body relative to each otherRight and left are retainedSuperior - up; synonymous with Cephalic, which means toward the head, because when we are in the anatomical position, the head is the highest pointInferior - down; synonymous with Caudal, which means toward the tail, which would be located at the end of the vertebral column if humans had tailsCephalic and caudal can be used to describe directional movements on the trunk, but they are not used to describe directional movements on the limbsProximal - nearestDistal - distantProximal and Distal are used to refer to linear structures such as the limbsAnterior - front; that which goes beforeVentral - bellyAnterior surface - ventral surface because the belly "goes first" when we are walkingPosterior - back; that which followsDorsal - backPosterior surface - dorsal surface because the back "follows" as we are walkingMedial - toward the midlineLateral - away from the midlineSuperficial - refers to a structure close to the surface of the bodyDeep - toward the interior of the bodyBody Parts and RegionsUpper Limb - divided into the arm, forearm, wrist, and hand

Arm - extends from the shoulder to the elbowForearm - extends from the elbow to the wrist

Lower Limb - divided into the thigh, leg, ankle, and footThigh - extends from the hip to the kneeLeg - extends from the knee to the ankle

Central Region - consists of the head, neck, and trunkTrunk - can be divided into the thorax (chest), abdomen (region between the thorax and the pelvis), and pelvis (the inferior end of the trunk associated with the hips)Abdomen - subdivided into four quadrants by two imaginary lines (one horizontal and one vertical) that intersect at the navel; the quadrants - right-upper, left-upper, right-lower, left-lower quadrants

- subdivided into nine regions by four imaginary lines (two horizontal and two vertical); the regions - epigastric, right and left hypochondriac, umbilical, right and left lumbar, hypogastric, and right and left iliac

Clinicians use the quadrants or regions as reference points for locating the underlying regionsPlanes

Sagittal Plane - runs vertically through the body and separates it into right and left parts; literally means the flight of an arrow and refers to the way the body would be split by an arrow passing anteriorly to posteriorlyMedian Plane - sagittal plane that passes through the midline of the body and divides it into equal right and left halvesTransverse (Horizontal) Plane - runs parallel to the surface of the ground and divides the body into superior and inferior partsFrontal (Coronal) Plane - runs vertically from right to left and divides the body into anterior and posterior partsLongitudinal Section - cut through the long axis of the organCross (Transverse) Section - cut at a right angle to the long axisOblique Section - cut is made across the long axis at other than a right angleBody CavitiesThoracic Cavity - rib cage surrounds it; muscular diaphragm separates it from the abdominal cavityMediastinum - median structure that divides the thoracic cavity into right and left parts; partition containing the heart, thymus, trachea, esophagus, and other structures; the two lungs are located on either side of the mediastinumAbdominal Cavity - abdominal muscles primarily enclose this, which contains the stomach, intestines, liver, spleen, pancreas, and kidneysPelvic Cavity - pelvic bones encase this small space, where the urinary bladder, part of the large intestine, and the internal reproductive organs are housedAbdominal and pelvic cavities are sometimes called the abdominopelvic cavitySerous MembranesCover the organs of the trunk cavities and line the trunk cavitiesVisceral Serous Membrane - inner wall in contact with the organParietal Serous Membrane - outer wallSerous Fluid - thin, lubricating film produced by the membranes that fills the cavity or space between the visceral and parietal serous membranesReduce friction between organsThoracic cavity contains three serous membrane-lined cavities: a pericardial and two pleural cavities

1. Pericardial Cavity - surrounds the heart; located between the visceral pericardium and the parietal pericardium and contains pericardial fluid

- visceral pericardium covers the heart, which is contained within a connective tissue sac lined with the parietal pericardium

2. Pleural Cavity - surrounds each lung; located between the visceral and parietal pleura and contains pleural fluid

- covered by visceral pleura and the parietal pleura lines the inner surface of the thoracic wall, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm

Abdominopelvic cavity contains a serous membrane-lined cavity called the peritoneal cavityVisceral peritoneum - covers many of the organs of the abdominopelvic cavityParietal peritoneum - lines the wall of the abdominopelvic cavity and the inferior surface of the diaphragmPeritoneal Cavity - located between the visceral peritoneum and the parietal peritoneum and contains peritoneal fluid

Inflammation of Serous Membranes 1. Pericarditis - inflammation of the pericardium2. Pleurisy - inflammation of the pleura3. Peritonitis - inflammation of the peritoneum

Mesenteries - consist of two layers of peritoneum fused together, connect the visceral peritoneum of some abdominopelvic organs to the parietal peritoneum on the body wall or to the visceral peritoneum of other abdominopelvic organs

- anchor the organs to the body wall and provide a pathway for nerves and blood vesels to reach the organs- parietal peritoneum covers these other organs, which are said to be retroperitoneal-retroperitoneal organs include the kidneys, the adrenal glands, the pancreas, parts of the intestines, and the urinary bladder