Introduction to the Human Body

## Overview of Anatomy and Physiology

**Anatomy:** scientific study of the body's structures

* ***Gross anatomy (macroscopic anatomy):*** study of the larger structures of the body, those visible without the aid of magnification
* ***Microscopic anatomy:*** study of structures that can be observed only with the use of a microscope or other magnification devices
* ***Regional anatomy:*** study of the interrelationships of all the structures in a specific body region
* ***Systemic anatomy:*** study of the structures that make up a discrete body system

**Physiology:** scientific study of the chemistry and physics of the strucutres of the body and the ways in which they work together to support the functions of life

**Homeostasis:** state of steady internal conditions maintained by living things

## Structural Organization of the Human Body

**Cell:** smallest independently functioning unit of a living organism

* ***Cytoplasm:*** water-based cellular fluid
* ***Organelle:*** variety of tiny functioning units within a cell

**Tissue:** group of many similar cells that work together to perform a specific function

**Organ:** anatomically distinct structure of the body composed of two or more tissue types

**Organ system:** group of organs that work together to perform major functions or meet physiological needs of the body

* ***Integumentary system:***
	+ encloses internal body structures
	+ sites of many sensory receptors
* ***Skeletal system:***
	+ supports the body
	+ enables movement (with muscular system)
* ***Muscular system:***
	+ enables movement (with skeletal system)
	+ helps maintain body temperature
* ***Nervous system:***
	+ detects and processes sensory information
	+ activates bodily responses
* ***Endocrine system:***
	+ ​​​​​​​secretes hormones
	+ regulates bodily processes
* ***Cardiovascular system:***
	+ ​​​​​​​delivers oxygen and nutrients to tissues
	+ equalizes temperature in the body
* ***Lymphatic system:***
	+ ***​​​​​​​***returns fluid to blood
	+ defends against pathogens
* ***Respiratory system:***
	+ ***​​​​​​​***removes carbon dioxide from the body
	+ delivers oxygen to blood
* ***Digestive system:***
	+ ​​​​​​​processes food for use by the body
	+ removes wastes from undigested food
* ***Urinary system:***
	+ ​​​​​​​controls water balance in the body
	+ removes wastes from blood and excretes them
* ***Male reproductive system:***
	+ produces sex hormones and gametes
	+ delivers gametes to female
* ***Female reproductive system:***
	+ ​​​​​​​produces sex hormones and gametes
	+ supports embryo/fetus until birth
	+ produces milk for infant

**Organism:** living being that has a cellular structure and that can independently perform all physiologic functions necessary for life

## Functions of Human Life

**Metabolism:** sum of all anabolic and catabolic reactions that take place in the body

* ***Anabolism:*** process whereby smaller, simpler molecules are combined into larger, more complex substances
	+ utilizes energy
* ***Catabolism:*** process by which larger, more complex substances are broken down into smaller, simpler molcules
	+ releases energy
* ***Adenosine triphosphate (ATP):*** chemical compound used to store and release energy

**Responsiveness:** ability of an organism to adjust to changes in its internal and external environments

**Development:** all of the changes the body goes through in life

* ***Differentiation:*** unspecialized cells become specialized in structure and function to perform certain tasks in the body

**Growth:** increase in body size

**Reproduction:** formation of a new organism from parent organisms

## Requirements for Human Life

**Oxygen**

* brain cells are especially sensitive to lack of oxygen due to their requirement for a high and steady production of ATP
* brain damage likely within 5 minutes without oxygen
	+ death likely within 10 minutes

**Nutrient:** substance in foods and beverages that is essential to human survival

* ***Water***
	+ ​​​​​​​can only survive a few days without water
	+ makes up 70% of an adult's body mass
	+ helps regulate internal temperature and cushions, protects, and lubricates joints and other body structures
* ***Macronutrients***
	+ ​​​​​​​energy-yielding nutrients are primarily carbohydrates and lipids
	+ proteins mainly supply the amino acids
	+ can survive without energy-yielding nutrients for several weeks
* ***Micronutrients***
	+ ​​​​​​​vitamins and minerals
	+ some can be stored, thus can survive without them for a few days or weeks
	+ other cannot be stored, so they must be consumed every day or two

**Temperature**

* chemical reactions in the body can only take place just above/below 37 degrees Celsius
* sweating is body's response to heat
	+ adequate water intake required when sweating
	+ less effective in humid environments since sweat cannot evaporate
* shivering is body's response to cold
* increased breakdown of stored energy
	+ when energy reserve is depleted, core temperature significantly drops and RBC's lose ability to give up oxygen
	+ causes confusion, lethargy, loss of consciousness, death
* body reduces blood flow to extremities
	+ can lead to frostbite and gangrene

**Pressure:** force exerted by a substance that is in contact with another substance

* altitude sickness results from less pressure at high altitudes, reducing exchange of gases
	+ causes dyspnea, confusion, headache, lethargy, and nausea

## Homeostasis

**Set point:** physiological value around which the normal range fluctuates

**Normal range:** restricted set of values that is optimally healthful and stable

**Negative feedback:** mechanism that reverses a deviation from the set point

* ***Sensor (receptor):*** component of a feedback system that monitors a physiological value
* ***Control center:*** component in a feedback system that compares the value to the normal range
* ***Effector:*** component in a feedback system that causes a change to reverse the situation and return the value to the normal range
* examples include blood glucose and sweating

**Positive feedback:** mechanism that intensifies a change in the body's physiological condition rather than reversing it

* example includes childbirth and penetrating wounds

## Anatomical Terminology

**Anatomical position:** body standing upright with the feet at shoulder width and parallel, toes forward; upper limbs are held out to each side, and the palms of the hands face forward

**Prone:** face-down orientation

**Supine:** face-up orientation

**Directional terms**

* ***Anterior (ventral):*** front or direction toward the front of the body
* ***Posterior (dorsal):*** back or direction toward the back of the body
* ***Superior (cranial):*** above or higher than another part of the body
* ***Inferior (caudal):***below or lower than another part of the body
* ***Lateral:*** direction toward the side of the body
* ***Medial:*** direction toward the middle of the body
* ***Proximal:*** position on a limb that is nearer to the point of attachment or the trunk of the body
* ***Distal:*** position on a limb that is further from the point of attachment or the trunk of the body
* ***Superficial:***closer to the surface of the body
* ***Deep:*** farther from the surface of the body

**Body planes**

* ***Sagittal plane:*** plane that divides the body or an organ vertically into right and left sides
	+ ***Midsagittal (median) plane:*** plane that runs directly down the middle of the body
	+ ***Parasagittal (longitudinal) plane:*** plane that divides the body into unequal left and right sides
* ***Frontal (coronal) plane:*** plane that divides the body or an organ into a front and rear portion
* ***Transverse plane (cross section):*** plane that divides the body or an organ horizontally into upper and lower portions

**Body cavities**

* ***Dorsal (posterior) cavity:*** contains the brain and spinal cord
	+ ***​​​​​​​Cranial cavity:*** contains the brain
	+ ***Vertebral (spinal) cavity:*** contains the spinal cord
* ***Ventral (anterior) cavity:*** abdominal and thoracic cavities
	+ ***​​​​​​​Thoracic cavity:*** superior subdivision
		- ***​​​​​​​Superior mediastinum***
		- ***Pleural cavity***
		- ***Pericardial cavity***
	+ ***Abdominal cavity:*** abdomen
	+ ***Pelvic cavity:*** most inferior part of the abdomen

**Abdominal regions**

 right lumbar
 right iliac

**Abdominal quadrants**

 right lower quadrant (RLQ)

**Membranes**

* ***Serous membrane:*** one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities
	+ ***Parietal layer:*** lines the walls of the body cavity
	+ ***Visceral layer:*** lines the organs
	+ ***Pleura:*** serous membrane surrounding the lungs
	+ ***Pericardium:***serous membrane surrounding the heart
	+ ***Peritoneum:*** serous membrane surrounding organs of the abdominopelvic cavity

## Medical imaging

**X-ray:** form of high energy EM radiation with a short wavelength capable of penetrating solids and ionizing gases

* best used to visualize hard structures
* can damage cell and cause cancer

**Computed tomography (CT):** noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about bodily structures

* especially useful for soft tissue scans
* exposes patients to a high dose of radiation

**Magnetic resonance imaging (MRI):** noninvasive medical imaging technique based on a phenomenon of nuclear physics in which matter exposed to magnetic fields and radio wavees was found to emit radio signals

* malignant tissue gives off different signals
* higher costs, patient discomfort

**Positron emission tomography (PET):** medical imaging technique involving the use of radiopharmaceuticals

* can illustrate physiologic activity

**Ultrasonography:** imaging technique that uses the transmission of high-frequency sound waves into the body to generate an echo signal that is converted by a computer into a real-time image

* least invasive of all techniques