The Human Body: An Orientation



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The Human Body: An Orientation

  • Chapter 1

Definitions

  • Anatomy - The study of the structure of body parts and their relationships to one another.
  • Physiology - The study of the function of living organisms.

Topics of Anatomy

  • Gross Anatomy
    • The study of large body structures visible to the naked eye

Topics of Anatomy

  • Regional Anatomy
    • The study of all structures (blood vessels, nerves, muscles) located in a particular region of the body

Topics of Anatomy

  • Systemic Anatomy
    • The gross anatomy of the body studied system by system

Topics of Anatomy

  • Surface Anatomy
    • The study of internal body structures as they relate to the overlying skin

Topics of Anatomy

  • Microscopic Anatomy
    • The study of structures too small to be seen without the aid of a microscope

Topics of Anatomy

  • Cellular Anatomy
    • The study of cells of the body

Topics of Anatomy

  • Histology
    • The study of the microscopic structure of tissues

Topics of Anatomy

  • Developmental Anatomy
    • The study of changes in an individual from conception to old age

Topics of Anatomy

  • Embryology
    • The study of the developmental changes that occur before birth

Complementarity of Structure and Function

  • The principle of complementarity of structure and function implies that function is dependent upon structure
    • Anatomy and physiology are truly inseparable sciences
    • In architecture “form follows function”
    • A description of anatomy is followed by an explanation of its function, the structural characteristics contributing to that physiologic function

Levels of Structural Complexity

  • Chemical
  • Molecules
  • Cells
  • Tissue
  • Organ
  • Organ System
  • Organism

Levels of Structural Complexity

  • Chemical Level
    • The simplest level of structural organization

Levels of Structural Complexity

  • Molecules
    • Building blocks of matter that combine to form water, sugar and proteins

Levels of Structural Complexity

  • Cellular Level
    • The smallest units of living tissue
    • In this example the tissue is smooth muscle fiber

Levels of Structural Complexity

  • Tissue Level
    • Consists of groups of similar cells that have a common function
      • epithelium
      • muscle
      • connective
      • nervous

Levels of Structural Complexity

  • Organ Level
    • A structure composed of at least two tissue types (with four the most common) that performs a specific function for the body

Levels of Structural Complexity

  • Organ System Level
    • Organs that cooperate with one another to perform a common function

Levels of Structural Complexity

  • Organism Level
    • The highest level of organization, the living organism

Organ Systems

  • The 11 human organ systems
    • Integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive

Maintaining Life Functions

  • Maintenance of Boundaries
  • Movement
  • Responsiveness
  • Digestion
  • Metabolism
  • Excretion
  • Reproduction
  • Growth

Maintaining Life Functions

  • Maintenance of boundaries
  • Every organism must control its internal environment
  • Need for selectively permeable membranes
  • Protection from external environment

Maintaining Life Functions

  • Movement
  • All voluntary movement of skeletal muscles
  • All movements of the involuntary muscles
  • Dependent upon the muscle cell being able to contract

Maintaining Life Functions

  • Responsiveness
  • The ability to sense changes in the environment and to react to the changes
  • The nervous system is the primary example
  • Related also to learning to monitor key stimuli

Maintaining Life Functions

  • Digestion
  • The process of breaking down food stuffs for absorption
  • The digestive system does this for the entire body
  • The circulatory system distributes the nutrients

Maintaining Life Functions

  • Metabolism
  • Encompasses the chemical reactions of the body
  • It includes breaking down molecules of food as well as forming new structures
  • Regulated in large part by hormones

Maintaining Life: Functional Characteristics

  • Excretion
  • The process of removing wastes from the body
  • Several systems often participate to carry out this process
  • Necessary in order to maintain internal environment

Maintaining Life Functions

  • Reproduction
  • Can occur at the cellular or organism level
  • Cellular reproduction is for tissue repair
  • Organism reproduction is for procreation
  • There exists a division of labor of this function

Maintaining Life Functions

  • Growth
  • An increase in the size of the body part or organism
  • Accomplished by increasing the number of cells
  • Cell increase must be at a faster rate than cell loss

Survival Needs

  • Nutrients
  • Oxygen
  • Water
  • Body Temperature
  • Atmospheric pressure

Survival Needs

  • Nutrients
  • Substances used for energy and cell building
  • Carbohydrates are fuel for body cells
  • Proteins for building cell structures
  • Fats for insulation and energy reserves
  • Minerals & vitamins for chemical reaction

Survival Needs

  • Oxygen
  • Oxygen needed for chemical reactions
  • Cells will survive only a few minutes without oxygen
  • Made available by the respiratory and cardiovascular systems

Survival Needs

  • Water
  • It provides the environment for chemical reactions
  • Fluid base for body secretions and excretions
  • Obtained by foods and liquids ingested
  • Lost by evaporation from skin and lungs

Survival Needs

  • Body temperature
  • Body temperature must be maintained for chemical reaction
  • Too low, reactions will slow or stop
  • Too high, chemical reactions occur at a rate that causes body proteins to lose their shape and stop functioning

Survival Needs

  • Atmospheric pressure
  • Breathing and air exchange is dependent on appropriate pressure
  • Inadequate pressure limits the ability of the body to support metabolism

Homeostasis

  • Definition
  • Control Mechanisms
  • Negative feedback
  • Positive feedback
  • Homeostatic imbalances

Homeostasis

  • The ability of the body to maintain relatively stable internal conditions even though there is continuous change in the outside world
    • A state of dynamic equilibrium
    • The body functions within relatively narrow limits
    • All body systems contribute to its maintenance

Control Mechanisms

  • Regardless of the factor or event (variable) being regulated, all homeostatic control mechanisms have at least three interdependent components
    • Receptor (stimuli of change is detected)
    • Control center (determines response)
    • Effector (bodily response to the stimulus)

Control Mechanisms

  • Regulation of homeostasis is accomplished through the nervous and endocrine systems

Control Mechanisms

  • A chain of events . . .
    • Stimulus produces a change in a variable
    • Change is detected by a sensory receptor
    • Sensory input information is sent along an afferent pathway to control center
    • Control center determines the response
    • Output information sent along efferent pathway to activate response
    • Monitoring of feedback to determine if additional response is required

Negative Feedback Mechanisms

  • Most control mechanisms are negative feedback mechanisms
  • A negative feedback mechanism decreases the intensity of the stimulus or eliminates it
  • The negative feedback mechanism causes the system to change in the opposite direction from the stimulus
    • Example: home heating thermostat

Positive Feedback Mechanisms

  • A positive feedback mechanism enhances or exaggerates the original stimulus so that activity is accelerated
  • It is considered positive because it results in change occurring in the same direction as the original stimulus
  • Positive feedback mechanisms usually control infrequent events such as blood clotting or childbirth

Positive Feedback Mechanism

  • Break or tear in blood vessel wall
  • Clotting occurs as platelets adhere to site and release chemicals
  • Released chemical attract more platelets
  • Clotting proceeds until break is sealed by newly formed clot

Homeostatic Imbalances

  • Most diseases cause homeostatic imbalances (chills, fevers, elevated white blood counts etc)
  • Aging reduces our ability to maintain homeostasis
    • Heat stress

The Language of Anatomy

  • Anatomical position
  • Directional terms
  • Regional terms
  • Body planes and sections
  • Body cavities and membranes
  • Abdominopelvic regions and quadrants

Anatomical Position

  • Anatomical position
  • Directional terms are used to describe a body structure or limb segment as it relates to the anatomical position

The Language of Anatomy:

  • Superior Toward the head end or upper part of a structure or the body
  • Inferior Away from the head end or toward the lower part of a structure or the body

The Language of Anatomy:

  • Anterior Toward or at the front of the body (ventral)
  • Posterior Toward the back of the body; behind (dorsal)

The Language of Anatomy:

  • Medial Toward or at the midline of the body
  • Lateral Away from the midline of the body
  • Intermediate Between a more medial and a more lateral structure

The Language of Anatomy:

  • Proximal Closer to the origin of the body part, or the point of attachment of a limb to the body trunk
  • Distal Farther from the origin of a body part or the point of attachment of a limb to the body trunk

The Language of Anatomy:

  • Superficial Toward or at the body surface
  • Deep away from the body surface; more internal

Regional terms

  • There are two fundamental divisions of our body
    • Axial
      • Head,
      • Neck
      • Trunk
    • Appendicular
      • Shoulder / Arm
      • Pelvis / Leg
  • Regional terms are used to designate specific areas within the major body divisions
    • Carpal / wrist
    • Oral / mouth
    • Femoral / thigh
    • Refer to Figure 1.7

Body Planes and Sections

  • In anatomy, the body is sectioned along a flat surface called a plane
  • The most frequently used body planes are sagittal, frontal and transverse which are at right angles to each other

Body Planes

  • The sagittal plane lies vertically and divides the body into right and left parts

Body Planes

  • The frontal plane divides the body into anterior and posterior sections
    • Also called a coronal

Body Planes

Body cavities and membranes

  • Dorsal body cavity
  • Ventral body cavity
  • Membranes
  • Other body cavities

Human Body Plan

  • All vertebrates share the same basic features
    • Tube-within-a- tube body plan
    • Bilateral symmetry
    • Dorsal hollow nerve cord
    • Notochord and vertebrae
    • Segmentation
    • Pharyngeal pouches

Human Body Plan

Tube-Within-A-Tube

  • Digestive organs form a tube that runs through the axial region of the body, which itself can be viewed as a larger tube

Bilateral Symmetry

  • Each body half is a mirror image of the other half
  • Structures in the midline plane are unpaired by symmetrical left and right sides

Dorsal Hollow Nerve Cord

  • All vertebrate embryos have a hollow cord running along their back in the median plane
  • The cord develops into the brain and spinal cord

Notochord and Vertebrae

  • The notochord is a stiffening rod in the back just deep to the spinal cord
  • The notochord in the embryo is replace by vertebrae

Segmentation

  • Segments are repeating units of similar structure that run from the head along the length of the trunk
  • Example: area between the ribs / spinal nerves

Pharyngeal Pouches

  • In humans the pharynx is part of the digestive tube
  • In the embryonic stage, our pharynx has a set of pouches that correspond to the clefts of fish gills

Pharyngeal Pouches

  • Pharyngeal pouches give rise to some structures in our head and neck
  • Example: The middle ear cavity which runs from the eardrum to the pharynx

Body Cavities

Body cavities

  • Dorsal body cavity is divided into a cranial cavity which encases the brain, and the vertebral cavity which encases the spinal cord

Body cavities

  • The ventral body cavity houses the visceral organs
  • The ventral body cavity is divided into the thoracic, abdominal, and pelvic cavities

Thoracic Cavity

  • The thoracic cavity is surrounded by the ribs and muscles of the chest
  • It is further divided into
    • plueral cavities
    • mediastinum
    • pericardial

Abdominopelvic Cavity

  • Abdominopelvic cavity lies below the diaphragm
  • It is further divided into . .
    • Abdominal cavity
      • Stomach, intestines, spleen, liver
    • Pelvic cavity
      • Bladder, rectum, and some reproductive organs

Membranes in Ventral Cavity

  • Serous membrane (serosa) is a thin double layered membrane that covers the ventral body cavity and outer surface of the organs
    • Parietal serosa is the layer of the membrane that lines the walls of the cavity
    • Visceral serosa is the layer that covers the organs in the cavity
    • Serous fluid is a lubrication found between the two serosa membranes

Membranes in the Ventral Cavity

  • Specific serous membranes are named for the cavity in which they are found
    • Parietal and visceral pericardium surrounds the heart
    • Parietal and visceral pleura surrounds the lungs
    • Parietal and visceral peritoneum covers the abdominal cavity

Serous Membrane Relationship

  • A serous membraneneeds to viewed as a double layer membrane separated by fluid

Serous Membrane Relationship

  • The serous membrane is a double layer separated by a thin lubricating fluid
  • The inner visceral layer covers the organ (heart, lung, etc)
  • The outer parietal layer lines the body cavity
  • Although there is a potential space in actuality the membranes lie close to one another

Other Body Cavities

  • In addition to the large, closed body cavities there are also many smaller body cavities
    • Oral and digestive cavities
    • Nasal cavities
    • Orbital cavities
    • Middle ear cavities
    • Synovival cavities

Other Body Cavities

Abdominopelvic Regions

  • Anatomists often divide the body cavity into nine smaller regions for study

Abdominopelvic Regions

  • Anatomists often divide the body cavity into nine smaller regions for study

Abdominal Quadrants

  • Medical personnel usually use a simpler scheme to localize and describe the condition of organs within the abdominopelvic cavity

The Human Body An Orientation



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