Chapter 1 Lecture Two The Language of Anatomy and Homeostasis

Anatomical Position Anatomical position – Standing up – Hands at the sides – Palms facing forward – Feet together Laying down in anatomical position – Supine (face up) – Prone (face down)

Directional Terms Describe relative position of a body part Terms occur in pairs with opposite meanings Uses the anatomical position –Upright body –Arms at sides with palms forward

Cranial Posterior or dorsal Anterior or ventral Caudal The principal directional terms Superior Inferior Right Left Proximal Lateral Medial Proximal Distal

Directional Terms anterior vs. posterior –The bellybutton is on the anterior surface proximal vs. distal –The elbow is proximal to the wrist superior vs. inferior –The chin is inferior to the nose medial vs. lateral –The thumb is lateral to the pinky finger

Body Planes and Sections Body planes are imaginary flat surfaces that pass through the body at right angles to each other Important to understand the three- dimensional structure of an observed object

Transverse plane –Divides body into superior and inferior portions Sagittal plane –Divides the body into right and left portions –Midsagittal (medial) plane –Parasagittal plane Frontal (coronal) plane –Divides the body into anterior and posterior portions

Planes - Overview

Body Cavities A body cavity is a space within the body and contains internal organs Two essential functions –Protect delicate organs from shocks and impacts –Permit significant changes in size and shape of internal organs There are two major body cavities –Dorsal cavity (posterior) –Ventral cavity (anterior)

Body Cavities

Abdominopelvic Subdivisions Abdomen can be divided into four quadrants –RUQ - Right Upper Quadrant –LUQ - Left Upper Quadrant –RLQ - Right Lower Quadrant –LLQ - Left Lower Quadrant

Quadrants and Organs RUQ – liver, gallbladder, right kidney LUQ – stomach, spleen, pancreas, left kidney RLQ – appendix, right ovary LLQ – left ovary

Module 1.10 Review a. Describe two essential functions of body cavities. b. Identify the subdivisions of the ventral body cavity. c. If a surgeon makes an incision just inferior to the diaphragm, what body cavity will be opened?

Homeostasis The ability of the body to maintain a constant internal environment within physiological set- points.

Parameters Maintained in Homeostasis gas concentrations –oxygen, carbon dioxide body temperature blood pressure pH (acidity) –blood, urine nutrients –glucose, sodium, potassium water

Normal condition restored Normal condition disturbed Sends commands to Information affects Thermometer Air conditioner turns on RESPONSE: Room temperature drops STIMULUS: Room temperature rises EFFECTOR RECEPTOR HOMEOSTASIS Normal room temperature CONTROL CENTER (Thermostat) The setting on a thermostat establishes the set point, or desired value, which in this case is the temperature you select. (In our example, the set point is 22°C, or about 72°F.) The function of the thermostat is to keep room temperature within acceptable limits, usually within a degree or so of the set point. Features of homeostatic control mechanisms, as shown for the maintenance of room temperature Figure 1 Section 3 1

Negative feedback –Effector opposes the original stimulus –Minimizes change –Primary mechanism of homeostatic regulation –Set point may vary with changing environments or activity levels

HOMEOSTASIS EFFECTORS RECEPTORS CONTROL CENTER Homeostasis restored Homeostasis disturbed At normal body temperature (set point: 37°C or 98.6°F), the temperature control center is relatively inactive; superficial blood flow and sweat gland activity are at normal levels. Homeostasis and body temperature Increased activity in the control center targets two effectors: (1) smooth muscle in the walls of blood vessels supplying the skin and (2) sweat glands. The smooth muscle relaxes and the blood vessels dilate, increasing blood flow through vessels near the body surface; the sweat glands accelerate their secretion. The skin then acts like a radiator by losing heat to the environment, and the evaporation of sweat speeds the process. If body temperature rises above 37.2°C (99°F), two sets of temperature receptors, one in the skin and the other within the brain, send signals to the homeostatic control center. The temperature control center receives information from the two sets of temperature receptors and sends commands to the effectors. Start The homeostatic control of body temperature, which involves a negative feedback loop

Positive feedback –Initial stimulus produces a response that exaggerates or enhances the change in the original conditions –Typically occurs when a potentially dangerous or stressful process must be completed quickly Example: clotting mechanism

Homeostasis and Disease Disease is the failure to maintain homeostatic conditions. It can start with a cell (cancer), a tissue, an organ…but will ultimately alter function or structure throughout the body

Module 1.7 Review a. Identify the components of homeostatic regulation. b. Explain the function of negative feedback systems. c. Why is positive feedback helpful in blood clotting but unsuitable for the regulation of body temperature?