Marieb A&P Chapter 1 Notes (The Human Body: An Orientation)

1.1 Form (Anatomy) Determines Function (Physiology)

  • Anatomy – Study of the structure of body parts and their relationships to one another

  • Physiology – Study of the function of the body; how body parts work to carry out life-sustaining activities

  • Reference values used in this textbook (for simplicity):

    • Reference male: a healthy, young male weighing about 155  lb155\ \,lb = 70 kg70\ kg
    • Reference female: a healthy, young female weighing about 125  lb125\ \,lb = 57 kg57\ kg

  • Anatomical Variability

    • Humans vary slightly in both external and internal anatomy
    • >90% of anatomical structures match textbook descriptions, but:
    • Nerves or blood vessels may be somewhat out of place
    • Small muscles may be missing
    • Extreme anatomical variations are seldom seen and are usually incompatible with life

  • Sex vs Gender

    • Sex: set of biological attributes based on chromosomes, gene expression, hormone action; reflected in reproductive anatomy and physiology – Male or female
    • Gender: psychosocial construct of behaviors, expressions, identities (man, woman, transgender, non-binary, etc.)

1.1 Form (Anatomy) Determines Function (Physiology) (continued)

  • The relationship between form and function underpins all physiological processes: what a structure can do depends on its form.

1.2 Topics of Anatomy (1 of 2)

  • Subdivisions of anatomy:
    • Gross (macroscopic) anatomy – study of large body structures visible to the naked eye
    • Regional anatomy – all structures in a particular area
    • System anatomy – one system (cardiovascular, nervous, muscular, etc.)
    • Surface anatomy – internal structures as they relate to overlying skin (visible muscle masses or veins on surface)

1.2 Topics of Anatomy (2 of 2)

  • Subdivisions of anatomy (continued)
    • Microscopic anatomy – structures too small to be seen with the naked eye
    • Cytology: study of cells
    • Histology: study of tissues
    • Developmental anatomy – structural changes throughout the life span
    • Embryology: developmental changes before birth

1.3 Studying Anatomy

  • Foundational skills:

    • Basic anatomical terminology
    • Observe, Manipulate, Palpate (feel organs with hands), Auscultate (listen with stethoscope)

  • Medical imaging technology – view inside the body without surgery:

    • X-ray
    • Magnetic Resonance Imaging (MRI)
    • Computed Tomography (CT)
    • Ultrasound

1.0 Topics of Physiology (overview tying to anatomy)

  • Subdivisions of physiology – Based on organ systems
    • Renal physiology: function of kidneys
    • Neurophysiology: function of nervous system
    • Cardiovascular physiology: function of heart and blood vessels
  • Often focuses on events at the cellular or molecular level
  • Studying physiology requires understanding basic chemical and physical principles (e.g., electrical currents, pressure, and lever systems)

Complementarity of Structure and Function

  • Anatomy and physiology are inseparable
  • Function always reflects structure; what a structure can do depends on its form
  • Principle: complementarity of structure and function

1.2 The Body’s Organization: From Atoms to the Whole Organism

  • Levels of structural organization (simplest to most complex):

    • Chemical level: atoms and molecules
    • Cellular level: cells and their organelles
    • Tissue level: groups of similar cells
    • Organ level: two or more types of tissues
    • Organ system level: organs that work closely together
    • Organismal level: all organ systems combined to make the whole organism

  • Example: cardiovascular system components illustrating levels of organization (Figure 1.2)

The Body’s Organ Systems and Their Major Functions (1 of 7)

  • The human body has 11 organ systems:

    • Integumentary
    • Skeletal
    • Muscular
    • Nervous
    • Endocrine
    • Cardiovascular
    • Lymphatic
    • Respiratory
    • Urinary
    • Digestive
    • Reproductive

  • Major functions are depicted in Figure 1.4 a–l; the slide set outlines how these systems coordinate to sustain life.

1.3 What Are the Requirements for Life? Necessary Life Functions (1 of 3)

  • Maintaining boundaries – Separation between internal and external environments must exist
    • Plasma membranes separate cells
    • Skin separates organism from environment
  • Movement – Of body parts via skeletal muscles; movement of cells; movement of substances (e.g., heart pumping blood)
    • Contractility: muscle cells’ ability to move by shortening
  • Responsiveness (excitability) – Ability to sense changes (stimuli) and respond
    • Examples: withdrawal reflex; breathing rate changes with activity
  • Digestion – Breakdown of ingested foodstuffs to simple molecules for absorption
  • Metabolism – All chemical reactions in body cells
    • Catabolism: breakdown of molecules
    • Anabolism: synthesis of molecules
    • Cellular respiration: using nutrients and oxygen to make energy (ATP)
    • ext{Catabolism} + ext{Anabolism}
      ightarrow ext{Metabolic energy (ATP)}
  • Excretion – Removal of wastes from digestion and metabolism
    • Urea, CO₂, feces
  • Reproduction – Cellular level: cell division for growth/repair; Organismal level: production of offspring
  • Growth – Increase in size of a body part or the organism

1.4 Homeostasis Is Maintained by Negative Feedback

  • Homeostasis: maintenance of relatively stable internal conditions despite external changes
  • Dynamic state of equilibrium: internal conditions are adjusted but kept within narrow limits
  • Law of mass balance: input = output for a substance to remain constant over time
    • extInput=extOutputext{Input} = ext{Output}
  • Maintained by contributions of all organ systems

Homeostatic Controls (Overview)

  • The nervous and endocrine systems are the two main regulatory systems
  • Variable: the factor being regulated (e.g., blood sugar, body temperature)
  • Three components of a homeostatic control system:
    • Receptor (sensor): monitors environment; responds to stimuli; sends input
    • Control center: determines set point and appropriate response; sends output
    • Effector: carries out response to restore balance; may be a muscle or gland; response reduces or enhances the original stimulus (negative vs positive feedback)

Homeostatic Controls (2 of 5)

  • Receptor – Monitors environment; responds to stimuli; sends information to control center (input)
  • Control center – Receives input; determines set point and response; sends information to effector (output)
  • Effector – Receives output from control center; provides means to respond (muscle or gland)
  • Response types:
    • Negative feedback: reduces or shuts off the original stimulus; brings variable back toward set point
    • Positive feedback: enhances the original stimulus (rare; cascade/amplification); examples include childbirth (labor) and blood clotting

Homeostatic Controls (3 of 5)

  • Negative feedback examples:

    • Regulation of body temperature (nervous system)
    • Regulation of blood glucose by insulin (endocrine system)

  • Figure 1.5 shows interactions among the elements of a homeostatic control system maintaining stable internal conditions.

Homeostatic Controls (4 of 5)

  • Positive feedback: example mechanisms that amplify a response
    • Labor contractions amplified by oxytocin
    • Platelet plug formation and blood clotting
  • This feedback is typically used for events that do not require ongoing adjustments

Homeostatic Controls (5 of 5)

  • Feedforward (anticipatory) responses – occur before a change in the internal environment
    • Example: before food is ingested, the smell can trigger saliva production and digestive juice release

Homeostatic Imbalance

  • Homeostatic imbalance: disturbance of homeostasis
    • Increases risk of disease
    • Contributes to aging; control systems become less efficient
    • If negative feedback systems are overwhelmed, destructive positive feedback may take over (e.g., heart failure)

1.5 Anatomical Terms Describe Body Directions, Regions, and Planes

  • Anatomical terminology – Used to describe specific areas and movements; helps accurate communication in health care and science

Anatomical Position and Directional Terms (1 of 2)

  • Anatomical position – Standard reference position: body erect, feet slightly apart, palms facing forward with thumbs pointing away from body

Anatomical Position and Directional Terms (2 of 2)

  • Directional terms describe one structure in relation to another
  • Direction is always based on the standard anatomical position
  • Right and left refer to the person being viewed, not the observer
  • Example: Ears are lateral to the nose

Orientation and Directional Terms (1 of 4) – Table 1.1 (Definitions and Examples)

  • Superior (cranial): toward the head end or upper part of a structure; above
    • Example: The head is superior to the abdomen
  • Inferior (caudal): away from the head end or toward the lower part; below
    • Example: The navel is inferior to the chin
  • Anterior (ventral): toward or at the front; in front of
    • Example: The breastbone is anterior to the spine
  • Posterior (dorsal): toward the back; behind
    • Example: The heart is posterior to the breastbone

Orientation and Directional Terms (2 of 4)

  • Medial: toward or at the midline; inner side
    • Example: The heart is medial to the arm
  • Lateral: away from the midline; outer side
    • Example: The arms are lateral to the chest
  • Intermediate: between a more medial and a more lateral structure
  • Proximal: closer to the origin of the body part or point of attachment to the trunk
    • Example: The elbow is proximal to the wrist
  • Distal: farther from the origin or point of attachment
    • Example: The knee is distal to the thigh
  • Superficial (external): toward or at the body surface
  • Deep (internal): away from the body surface; more internal
  • Note: In humans, ventral = anterior and dorsal = posterior; these terms have different meanings in four-legged animals

Orientation and Directional Terms (3 of 4) – Regional Terms (Overview)

  • Two major body divisions:
    • Axial: head, neck, trunk
    • Appendicular: limbs (arms and legs)
  • Regional terms designate specific areas within these divisions

Orientation and Directional Terms (4 of 4) – Regional Terms (Examples)

  • Cephalic, Otic, Occipital
  • Frontal, Orbital, Nasal, Buccal (cheek), Oral, Mental (chin)
  • Cervical, Thoracic, Sternal, Axillary, Mammary
  • Abdominal, Umbilical, Pelvic, Inguinal (groin), Pubic (genital)
  • Upper limb regions: Cephalic (not shown here), Acromial, Brachial, Antecubital, Olecranal, Antebrachial, Carpal, Manus, Metacarpal, Palmar, Pollex, Digital
  • Lower limb regions: Coxal (hip), Femoral (thigh), Patellar, Popliteal, Crural (leg), Sural (calf), Fibular (peroneal), Pedal (foot), Tarsal (ankle), Calcaneal, Metatarsal, Digital, Plantar, Hallux

Regional Terms (continued) – Visuals

  • (a) Anterior/Ventral view highlights regional terms such as Cephalic, Thorax, Abdomen, Pelvis, and limb regions
  • (b) Posterior/Dorsal view highlights back region terms and posterior limb regions

1.5 Body Planes and Sections (1 of 5)

  • Body plane – flat surface along which the body or its structures may be divided for anatomical study
  • Three most common body planes:
    • Sagittal
    • Frontal (coronal)
    • Transverse (horizontal)
  • Section – a cut through the body along a plane; named after plane (e.g., sagittal section)

Body Planes and Sections (2 of 5)

  • Sagittal plane – vertical plane dividing the body into right and left parts
    • Midsagittal (median) plane: exactly along the midline
    • Parasagittal plane: offset from the midline
    • Figure 1.9a shows planes and MRI scans

Body Planes and Sections (3 of 5)

  • Frontal (coronal) plane – vertical plane dividing the body into anterior (front) and posterior (back)
  • Produces a frontal (coronal) section when cut along this plane
  • Figure 1.9b shows planes with MRI scans

Body Planes and Sections (4 of 5)

  • Transverse (horizontal) plane – divides the body into superior (top) and inferior (bottom) parts
  • Produces a transverse (cross) section when cut along this plane
  • Figure 1.9c shows planes with MRI scans

Body Planes and Sections (5 of 5)

  • Oblique section – results from cuts other than at a right angle; seldom used and can be difficult to interpret

1.6 Many Internal Organs Lie in Membrane-Lined Body Cavities

  • The body contains internal cavities that are closed to the environment
  • Cavities provide different degrees of protection to the organs within them
  • Two sets of cavities:
    • Dorsal body cavity
    • Ventral body cavity

Dorsal Body Cavity

  • Protects the fragile nervous system
  • Subdivisions:
    • Cranial cavity – encases brain
    • Vertebral (spinal) cavity – encases spinal cord
  • Covered by membranes called meninges

Ventral Body Cavity (1 of 6)

  • Houses the internal organs (viscera)
  • Divided into two major cavities by the diaphragm:
    • Thoracic cavity
    • Two pleural cavities – each surrounds one lung
    • Mediastinum – contains other thoracic organs (thymus, parts of trachea and esophagus)
    • Contains pericardial cavity – encloses heart
    • Abdominopelvic cavity
    • Abdominal cavity – stomach, intestines, spleen, liver, etc.
    • Pelvic cavity – urinary bladder, reproductive organs, rectum

Ventral Body Cavity (2 of 6) – Serous Membranes

  • Serosa (serous membrane) – thin, double-layered membranes covering surfaces in the ventral body cavity
    • Parietal serosa lines cavity walls
    • Visceral serosa covers organs (viscera)
    • Slit-like cavity between membranes filled with lubricating serous fluid
    • Fluid secreted by both layers
    • Figure 1.11a shows serous membrane relationships

Ventral Body Cavity (3 of 6) – Specific Serous Membranes

  • Named for the cavity and organs they surround:
    • Pleura – parietal pleurae line pleural cavities; visceral pleurae cover lungs; pleural fluid between layers
    • Peritoneum – parietal peritoneum lines the abdominal wall; visceral peritoneum covers most abdominal/pelvic organs; contains peritoneal fluid
    • Pericardium – parietal pericardium lines the pericardial cavity; visceral pericardium covers the heart; contains pericardial fluid

Ventral Body Cavity (4 of 6) – Serous Membrane Relationships (Figure 1.11b)

  • Diagrammatic representation of how serous membranes wrap around organs in the ventral cavity

Ventral Body Cavity (5 of 6) – Serous Membrane Inflammation (Clinical)

  • Serous membranes can become inflamed due to infection or other causes
  • Inflammation can cause roughness and sticking between layers, causing excruciating pain
  • Examples:
    • Pleural inflammation = pleurisy
    • Peritoneal inflammation = peritonitis

Ventral Body Cavity (6 of 6) – Abdominopelvic Quadrants and Regions

  • Abdominopelvic quadrants (4): Right Upper Quadrant (RUQ), Left Upper Quadrant (LUQ), Right Lower Quadrant (RLQ), Left Lower Quadrant (LLQ)
  • Abdominopelvic regions (9): Umbilical, Epigastric, Pubic (Hypogastric), Right Inguinal (Iliac), Left Inguinal (Iliac), Right Lateral (Lumbar), Left Lateral (Lumbar), Right Hypochondriac, Left Hypochondriac
  • Figures 1.12 and 1.13 illustrate the quadrants and the nine-region scheme

1.7 Clinical—Homeostatic Imbalance 1.1

  • "Wrong site surgery" – critical surgical errors may arise from confusion about right vs left or terminology
  • Example: amputation of the wrong leg (e.g., removing the right leg instead of the left)

1.8 Other Body Cavities

  • Open cavities (exposed to environment):
    • Oral cavity (mouth) – teeth and tongue; continuous with digestive tract; ends at the anus
    • Nasal cavity – within and posterior to the nose; part of respiratory pathways
    • Orbital cavities – house the eyes
    • Middle ear cavities – contain tiny bones that transmit sound vibrations for hearing
  • Closed cavities (not exposed to environment):
    • Synovial cavities – enclosed within fibrous capsules around freely movable joints; synovial membrane secretes synovial fluid to lubricate joints

  • Summary of key ideas across the chapter:

    • Anatomy explains structure; physiology explains function; together they describe how the body works in an integrated manner.
    • The body’s organization follows a hierarchical structure from atoms to the organism, with specific organ systems performing distinct but integrated roles.
    • Homeostasis relies primarily on negative feedback to maintain stability, with positive feedback used for certain rapid, self-limiting processes.
    • A broad set of anatomical terms, planes, and cavity concepts provides a precise language for describing location, orientation, and relationships of body parts.
    • Awareness of potential clinical errors (e.g., wrong-site surgery) and the existence of various body cavities and membranes is crucial for safe medical practice.

  • LaTeX references for quick recall:

    • Reference values: 155 lb=70 kg155\,\text{lb} = 70\,\text{kg} and 125 lb=57 kg125\,\text{lb} = 57\,\text{kg}
    • Law of mass balance: Input=Output\text{Input} = \text{Output}
    • Energy metabolism relation: Catabolism+Anabolism→ATP\text{Catabolism} + \text{Anabolism} \rightarrow \text{ATP}