An Introduction to the Human Body

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An Introduction to the Human Body

• Anatomy
• science of structure
• Histology is study of microscopic aspect of
  anatomy
• Physiology
• science of body functions
• Normal adult physiology changes due to infection
  by pathogens (disease causing life forms) or
  disorder (malfunction due to genetic or other
  factors)

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Levels of Organization

• Chemical
• Cellular
• Tissue
• Organs
• System Level
• Organismic Level

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Levels of Structural Organization

• Chemical Level
• atomic and molecular level
• Cellular level
• smallest living unit of the body
• Tissue level
• group of cells and the materials surrounding them
  that work together on one task
• 4 basic tissue types
• epithelium, muscle, connective tissue, and nerve

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Levels of Structural Organization

• Organ level
• grouping of 2 or more tissue types into a
  recognizable structure with a specific function.
• System
• collection of related organs with a common
  function
• sometimes an organ is part of more than one
  system
• Organismic level
• one living individual.

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Homeostasis

• Maintaining the internal environment within
  physiological limits (may not be optimal level)
• Example Blood temperature is kept between
  100-104 oF(38oC), blood volume is kept between
  4-6 L (Male and female)
• Two systems that maintain homeostasis are
  Nervous system Endocrine system

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Control of Homeostasis

• Homeostasis is continually being disrupted by
• external stimuli or
• intense heat, cold, lack of oxygen, pathogenic
  microbes
• internal stimuli
• psychological stresses
• Organ/system malfunction, internal injury etc.
• Disruptions can be mild to severe
• If homeostasis is not maintained, death may result

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Feedback Loop

• Feed back loop is the way of communication to
  maintain homeostasis. Components are
• Receptor
• Structures that monitor a controlled condition
  and detect changes
• Control center
• determines next action
• Effector
• receives directions from the control center
• produces a response that restores the controlled
  condition

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Feed Back Loop
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Feedback Loops Types

• Negative feedback loop
• original stimulus reversed
• most feedback systems in the body are negative
• used for conditions that need frequent adjustment
• Positive feedback loop
• original stimulus intensified
• seen during normal childbirth

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Homeostasis of Temperature

• Thermo receptors in walls of blood vessels detect
  an increase in temp. during exercise
• Brain receives input and signals blood vessels
  and sweat glands
• Blood vessels dilate (increase in diameter),
  sweat released.
• Loss of heat by combined action. Temperature
  turns to normal

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Positive Feedback during Childbirth

• Stretch receptors in walls of uterus send signals
  to the brain
• Brain induces release of hormone (oxytocin) into
  bloodstream
• Uterine smooth muscle contracts more forcefully
• More stretch, more hormone, more contraction etc.
• Cycle ends with birth of the baby decrease in
  stretch

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Body Fluids

• Delineation of fluid compartments
• intracellular fluid (ICF) within cells
• extracellular fluid (ECF) outside
• cells
• - interstitial fluid
• - plasma fluid portion of blood
• Continuous exchange of substances between
  compartments
• nutrients, oxygen, ions and wastes

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Basic Anatomical Terminology

• Anatomical position
• Regions of the body
• Anatomical planes, sections and directional terms

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Anatomical Position

• Standardized position from which to describe
  directional terms
• standing upright
• facing the observer, head level
• eyes facing forward
• feet flat on the floor
• arms at the sides
• palms turned forward

anatomical position?
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Common Regional Names
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Planes and Sections

• A plane is an imaginary flat surface that passes
  through the body.
• A section is one of the 2 surfaces (pieces) that
  results when the body is cut by a plane passing
  through it.

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Frontal Plane

• Frontal or coronal plane
• divides the body or an organ into front
  (anterior) and back (posterior) portions

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Sagittal Plane

• Sagittal plane
• divides the body or an organ into left and right
  sides
• Midsagittal plane
• produces equal halves

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Transverse Plane

• divides the body or an organ into upper
  (superior) or lower (inferior) portions

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Major Directional Terms
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Superior or Inferior

• Superior
• towards the head
• The eyes are superior to the mouth.
• Inferior
• away from the head
• The stomach is inferior to the heart.

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Dorsal or Ventral

• Dorsal or Posterior
• at the back of the body
• The brain is posterior to the forehead.
• Ventral or Anterior
• at the front of the body
• The sternum is anterior to the heart.

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Medial or Lateral

• Medial
• nearer to the midline of the body
• The heart lies medial to the lungs.
• Lateral
• farther from the midline of the body
• The thumb is on the lateral side of the hand.

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Dorsal Body Cavities

• Near dorsal surface of body
• 1. cranial cavity
• holds the brain
• formed by skull
• 2. vertebral or spinal canal
• contains the spinal cord
• formed by vertebral column

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Ventral Body Cavities

• Near ventral surface of body
• thoracic cavity above diaphragm
• abdominopelvic cavity below diaphragm
• Diaphragm large, dome-shaped muscle
• Organs called viscera
• Many sub cavities are present ex. Nasal cavity
  oral cavity etc.

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Serous Membranes

• Thin slippery membrane lines body cavities not
  open to the outside. Always 2 layers
• parietal layer lines walls of cavities
• visceral layer covers viscera within the cavities
• Ex include pericardial membrane around heart,
  pleural membrane around lungs, peritoneum within
  abdomino-pelvic cavity etc.

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Epithelial membranes

• Line body cavities/canals open to exterior. Ex.
  Membrane lining nasal cavity, oral cavity,
  respiratory tract, urinary tract, vagina etc.
• Single layered and fast regenerating