Unit 1A&PObjective A&P8 min read

Body Organization, Terminology, and the Skin

Unit 1: Anatomy and Physiology. Lesson 1 of 60 in CBET Academy.

A biomed does not diagnose patients, but every device you touch measures or treats a body system, and every clinician you talk to uses the same vocabulary. This lesson gives you the map and the words.

How the body is organized

Cells form tissues (epithelial, connective, muscle, nervous), tissues form organs, and organs form systems. The exam names six systems: circulatory, respiratory, gastrointestinal, nervous, musculoskeletal, and endocrine, and four organs to know well: heart, lungs, brain, and skin.

Directions and positions

Anterior front, posterior back. Superior above, inferior below. Medial toward the midline, lateral away from it. Proximal closer to the trunk, distal farther away.
Supine lying face up, prone face down.
Planes: sagittal splits left and right, coronal (frontal) splits front and back, transverse splits top and bottom.

Medical word parts

Most terms are a root plus a prefix or suffix.

Prefixes: brady- slow, tachy- fast, hyper- above normal, hypo- below normal, a- or an- without, dys- difficult or abnormal.
Roots: cardio heart, pulmo or pneumo lung, nephro or reno kidney, hepat liver, neuro nerve, gastro stomach, derm skin, osteo bone, hemo blood, myo muscle, encephal brain.
Suffixes: -itis inflammation, -ectomy surgical removal, -ostomy surgical opening, -oscopy looking inside, -graphy recording, -gram the recording itself, -algia pain, -emia blood condition.

So tachycardia is a fast heart, an electrocardiogram is a recording of the heart's electricity, and hypoxemia is low oxygen in the blood.

Vital signs, the numbers you will see everywhere

Heart rate 60 to 100 beats per minute; below 60 bradycardia, above 100 tachycardia.
Respiratory rate 12 to 20 breaths per minute.
Blood pressure about 120/80 mmHg.
Oxygen saturation 95 to 100 percent.
Temperature 37 C (98.6 F); fever above about 38 C.

The skin

Three layers: the epidermis (outer barrier), the dermis (blood vessels, nerves, glands), and the subcutaneous fat. The skin protects against infection, regulates temperature, and senses touch and pain. For the biomed it matters three ways: electrodes must overcome skin impedance (skin prep and gel), electrosurgery and warming devices can burn it, and pressure from beds and cuffs can injure it.

Exam tip: word-part questions are free points. Break the word apart: brady (slow) + cardia (heart). Direction questions usually hinge on proximal versus distal and medial versus lateral.

Remember

Cells, tissues, organs, systems. Anterior front, posterior back, proximal near, distal far, supine up, prone down. Brady slow, tachy fast, hyper high, hypo low, -itis inflammation, -ectomy removal. Know the vital sign ranges.

Deeper explanation

Body Organization, Terminology, and the Skin, explained slowly

Why a biomed needs anatomy at all

You will never diagnose anyone. But a nurse will say "the art line waveform is damped," a physician will ask whether the monitor can show a lead II rhythm during a proximal femoral procedure, and a purchase request will call for a device to treat "hypothermia post-cardiac arrest." Every one of those sentences is built from the vocabulary in this lesson. Learn the vocabulary and the rest of the course, and the job, gets easier.

The body as a building

Think of the body as a building assembled from the ground up:

cells      the bricks
tissues    walls made of one kind of brick: epithelial (lining), connective (support), muscle, nervous
organs     rooms with a purpose: heart, lungs, brain, skin, kidneys
systems    the building's services: circulatory (plumbing), respiratory (ventilation),
           nervous (wiring), gastrointestinal (kitchen and waste), endocrine (thermostat), musculoskeletal (frame)

Directions: a map with two axes and a depth

Anatomical position is standing, facing you, palms forward. Every direction word is relative to that.

anterior / posterior   front / back                 the sternum is anterior, the spine is posterior
superior / inferior    above / below                the head is superior to the chest
medial / lateral       toward / away from midline   the nose is medial, the ears are lateral
proximal / distal      near / far from the trunk    the elbow is proximal to the wrist
supine / prone         face up / face down          patients on the OR table are usually supine

Planes cut the body into halves: sagittal (left and right), coronal or frontal (front and back), transverse (top and bottom). Imaging reports and OR table positions use these words constantly.

Word parts: a decoder ring

Medical words are assembled from parts, and the parts always mean the same thing. Decode from the end.

Prefix (how)          Root (what)             Suffix (what happened)
brady-  slow          cardi   heart           -itis     inflammation
tachy-  fast          pulmon  lung            -ectomy   removal
hyper-  too much      nephr   kidney          -ostomy   an opening
hypo-   too little    hepat   liver           -oscopy   looking in
a-/an-  without       neur    nerve           -graphy   recording (the act)
dys-    difficult     gastr   stomach         -gram     the recording itself
                      derm    skin            -algia    pain
                      oste    bone            -emia     in the blood
                      hem     blood
                      my      muscle

Worked examples: bradycardia = slow heart. Nephrectomy = kidney removal. Electrocardiogram = the record of the heart's electricity. Hypoxemia = too little oxygen in the blood. Gastroscopy = looking into the stomach. Apnea = without breathing. Dyspnea = difficult breathing.

Vital signs: the numbers on every monitor

Heart rate          60 to 100 bpm        under 60 bradycardia, over 100 tachycardia
Respiratory rate    12 to 20 per minute  apnea = none
Blood pressure      about 120/80 mmHg    hypertension high, hypotension low
SpO2                95 to 100 percent    hypoxemia below
Temperature         37 C / 98.6 F        fever above about 38 C

When a monitor is "reading wrong," the first question is whether the number is even plausible. A heart rate of 300 or an SpO2 of 40 on a comfortable patient is a device or lead problem, not a patient problem.

The skin, from the technician's side

Three layers: epidermis on top (dead, dry, a good insulator), dermis below (blood, nerves, sweat glands), subcutaneous fat beneath. It matters to you three ways:

Impedance: dry epidermis resists electricity, which is why electrodes need skin prep and conductive gel, and why a shock through dry skin is far less dangerous than through wet.
Burns: electrosurgery return pads, warming blankets, and hot lamps all injure skin when contact or temperature is wrong.
Pressure: beds, cuffs, and probes left too long cause pressure injuries; SCD sleeves and cuff cycling matter.

How the exam asks it

"The wrist is ___ to the elbow." Distal.
"Which term means slow heart rate?" Bradycardia.
"A patient lying face down is in which position?" Prone.
"Which layer of skin provides most of its electrical resistance?" The epidermis.

What to memorize

Cells, tissues, organs, systems. Anterior, posterior, superior, inferior, medial, lateral, proximal, distal, supine, prone.
The prefix, root, suffix table. Decode from the suffix backward.
Vital sign ranges.