The Human Body: An Orientation

Define Anatomy. What is the main subdivision?

Anatomy is the study of the structure of body parts and their relationship to one another- what they look like, where they are located, and how they are organized.

• Gross (macroscopic) anatomy: visible to the naked eye

  • Regional: all structure in a specific area (e.g., head, leg)

  • Systemic: body systems (e.g., cardiovascular)

  • Surface: study of visible landmarks to understand internal anatomy (e.g., taking a pulse or locating veins)

• Microscopic anatomy: needs a microscope

  • Cytology: study of cell

  • Histology: study of tissue

• Developmental anatomy: structural changes from conception to old age

  • Embryology: study of development before birth

Doctors often reply of surface anatomy to guide procedures life drawing blood or placing catheters.

Pathologists use histology to diagnose diseases from tissue samples.

Define Physiology.

How is it related to anatomy?


Physiology is the study of the function of the body parts- how body parts work and carry out life-sustaining activities.

It relies on the understanding of basic physical principles (like pressure and flow) and chemical properties.

Anatomy and physiology are inseparable: structure dictates function.

What are the six levels of structural organization, from simplest to most complex?

1. Chemical: atoms form molecules (e.g., water, proteins)

2. Cellular: molecules combine to form cells, the basic unit of life

3. Tissue: groups of similar cells performing common functions

4. Organ: two or more tissues form organs (e.g., the heart has muscle and connective tissue)

5. Organ systems: organs work together to perform complex functions

6. Organism: all systems combined make the whole living being

Example:

To breathe:

Molecules → lung cells → lung tissue → lungs (organ) → respiratory system → living person

What are the necessary life functions?


The human body must carry out eight key life functions to survive and function properly:

• Maintaining Boundaries- separates inside from outside

• cell membranes protect cells; skin protects the body

• Movement- of body and internal materials

• muscles move limbs, blood flows, food moves in digestive tract

• Responsiveness (Irritability)- detect & responsiveness to stimuli

• nervous system triggers actions like pulling away from pain

• Digestion- breakdown of food→ nutrients → into blood

• Metabolism- all chemical reaction in body

• includes:

• catabolism= breaking down

• anabolism= building up

• regulated by hormones

• Excretion- removing waste

• CO2 (lungs), urea(kidneys), feces (intestines)

• Reproduction- cell division (growth/repair) & producing offspring

• Growth- increase in cell size and/or number

What are the necessary life functions?


The human body must carry out eight key life functions to survive and function properly:

• Maintaining Boundaries- separates inside from outside

• cell membranes protect cells; skin protects the body

• Movement- of body and internal materials

• muscles move limbs, blood flows, food moves in digestive tract

• Responsiveness (Irritability)- detect & responsiveness to stimuli

• nervous system triggers actions like pulling away from pain

• Digestion- breakdown of food→ nutrients → into blood

• Metabolism- all chemical reaction in body

• includes:

• catabolism= breaking down

• anabolism= building up

• regulated by hormones

• Excretion- removing waste

• CO2 (lungs), urea(kidneys), feces (intestines)

• Reproduction- cell division (growth/repair) & producing offspring

• Growth- increase in cell size and/or number

Survival Needs

What basic things does the body require to survive?


• Nutrients- for energy & cell building

• carbs= fuel, protein= structure, fats= storage

• Oxygen- needed for aerobic energy production (ATP)

• Water- vital for chemical reactions; makes up 60%-80% of body

• Normal body temperature (~98.6F)- for proper enzyme function

• too low= reactions slow; too high= proteins denature

• Atmospheric pressure- needed for breathing

Define homeostasis. What keeps it stable?


Homeostasis: stable internal environment (body stays balanced)

• keeps body conditions (e.g., temp, blood sugar) within healthy range

Homeostatic Control Mechanism:

• receptor- senses change

• control center- processes info & plans response (usually brain)

• effecter- carries out the fix

Communication:

• afferent pathway= to control center

• efferent pathway= from control center

Feedback Mechanisms

How do negative and positive feedback differ in maintaining balance?


Negative Feedback:

• reverses a change to return to normal

• most common type

example: blood glucose rises→ insulin released → glucose drops

Positive Feedback:

• amplifies the change until task is done

• short-term, not for daily balance

example: labor → oxytocin ↑ → stronger contractions → birth

Too much positive feedback= dangerous (e.g., high fever spirals)

Anatomical Position & Directional Terms


Anatomical Position:

• body upright

• facing forward

• arms at sides, palms forward

• feet slightly apart

Directional Terms:

• Superior- toward head

• Inferior- away from head

• Anterior (ventral)- front side

• Posterior (dorsal)- back side

• Medial- toward midline

• Lateral- away from midline

• Proximal- closer to limb origin

• Distal- farther from origin

• Superficial- near surface

• Deep- farther inside

Body Planes and Sections


Body planes: imaginary flat surfaces used to cut the body for viewing structures:

• Sagittal plane- divides body into left and right

• midsagittal: equal halves

• parasagittal: unequal halves

• Frontal plane (coronal)- divides into front (anterior) and back (posterior)

• Transverse plane (horizontal)- divides into top (superior) and bottom (inferior)

• creates a cross-section view

Oblique section: cuts made diagonally (less common)

Body Cavities & Membranes

What are the major body cavities and what membranes line them?


Dorsal Body Cavity (back side)

• cranial cavity: brain

• vertebral cavity: spinal cord

• lined by meninges

Ventral Body Cavity (front side)

• thoracic cavity: lungs, heart

• pleural cavities: each lung

• pericardial cavity: heart

• abdominopelvic cavity:

• abdominal: stomach, liver, intestines

• pelvic: bladder, reproductive organs

Serous Membranes (thin, double-layered)

• parietal layer: lines cavity wall

• visceral layer: covers the organ

• fluid in between reduces friction

What are regional terms?


Regional terms help identify specific body parts:

axial: main axis (head, neck, trunk)

appendicular: limbs (arms & legs)