The Human Body

Anatomy – the study of the structure of the body parts and their relationships to one another.

Physiology – the function of the body and how the parts work.

Overview of Anatomy and Physiology

1. Gross: (macroscopic) anatomy is the study of the large body structures visible to the naked eye.

◦ Regional: is the study of all the structures in one particular part of the body at the same time. (bones, muscles, nerves, blood vessels, etc. in the leg)

◦ Systematic: is the study of the body by systems (respiratory system, nervous system)

◦ Surface: is the study of internal body structures as they relate to the overlying skin surface (bulging muscles, finding a blood vessel for a pulse, etc.)

Subdivisions of Anatomy

2. Microscopic anatomy is the study of structures too small to be seen without a microscope.

◦ Cytology: the study of cells◦ Histology: the study of tissues

3. Developmental anatomy is the study of structural changes in an individual

◦ Embryology is the study of changes that occur before birth

1. Pathological anatomy looks at structural changes (either gross or microscopic levels) that occur as a result of disease.

2. Radiographic anatomy looks at internal structures (tumors and bone disorders) that change gross anatomy based on x-ray or other scanning procedures.

3. Molecular biology studies the structure of the biological molecules (especially on a subcellular level)

Other highly specialized forms of anatomy used for diagnosis

Observation – observing how the parts of the knee joint fit together

Manipulation – manipulating the joint to determine range of motion

Mastery of anatomical terminology – using anatomical terminology to name its parts and describe how they are related.

The three most important tools to study anatomy are

The operation of specific organ systems◦ Renal physiology (urine production and kidney

function)◦ Neurophysiology (function of the nervous system)◦ Cardiovascular physiology (heart/blood vessel

functions)

Subdivision of Physiology

Physiology often focuses on cellular or molecular levels because the body depends on the successful functioning of individual cells which in turn ultimately depends on the chemical reactions occurring inside each cell.

Physiology also deals with understanding physics (electrical charges are responsible for all nervous system and muscular system functions.

Bones support because of their hard mineral deposits

Blood flows in one direction thru the heart because valves prevent backflow

Lungs are the site of gas exchange because air sacs are moist and thin-walled

Principle of complementarity of structure and function

Simplest to most complex Chemical level – atoms build molecules

such as water, sugar and proteins which in turn form organelles.

Cellular shape – cells are the smallest unit of living things but the vary in shape, size, and sometimes function.

Levels of structural Organization

Tissue level: tissues are groups of cells that have a common function and a characteristic role in the body. There are 4 types.1. Epithelium – covers the body surface and lines

the cavities2. Muscle – provides movement3. Connective – supports the body and protects

organs4. Nervous – provides rapid internal

communication

Organs are composed of at least two different types of tissues. Four types are most common though. These provide a specific function for the body, sometimes extremely complex.◦ Stomach has several tissues:

1. Epithelium is the linning, mucus and glands2. Muscle is for churning and mixing3. Connective tissue supports the muscle4. Nervous tissue stimulates digestive activity

Organs

A singe bone or a single muscle is considered an organ.

Organ system level – composed of organs that work closely with one another to accomplish a common purpose.◦ Digestive system is the mouth, salivary glands,

esophagus, stomach, pancreas, liver, gall bladder, small intestine, large intestine and rectum.

Organismal level – the highest level of organization that represents the sum total of all structural levels working in unison.

In order to maintain necessary life function, organ systems must work together and cooperatively.

Maintaining Life

1. Maintaining boundaries – the internal environment must remain distinct and protected from the external environment. (integument keeps us from drying out and keeps harmful things out of our body – bacteria, chemicals, UV radiation.

2. Movement – includes all activities of the muscular system used for propulsion (walking, running, swimming), manipulation (using fingers or toes), and peristalsis (movement of foodstuffs and waste through the body)

8 Major Functional Processes

3. Responsiveness (irritability) – the ability to sense changes (stimuli) in the environment and respond to them suing the nervous system.

4. Digestion – the process of breaking down ingested foodstuffs into simple molecules (the digestive system) which are absorbed into the blood and transported to cells via the cardiovascular system.

5. Metabolism – includes all chemical reactions that occur in the body by the digestive system ( breaking down food molecules into simpler compounds), respiratory system (supplying oxygen to change simpler compounds into energy-rich molecules) and the circulatory system (moves oxygen and nutrients to all cells)

6. Excretion – the process of removing waste from the body by the digestive system (solid, indigestible food) the urinary system (nitrogenous waste like urea and uric acid), and the respiratory and circulatory systems (moving carbon dioxide to the lungs for exhalation).

7. Reproduction- occurs at both the cellular level (mitosis) and organismal level (using both the reproductive and endocrine systems)

8. Growth – an increase in the size of an organism usually accomplished by increasing the number of cells (sometimes the cell itself enlarges)

In order to survive in life several factors (survival needs) are required in appropriate amounts (deficits or excess may be harmful)

1. Nutrients – taken in through the diet and responsible for energy and cell-building.

◦ Carbohydrates (starch from plants, major source of energy)

◦ Protein (from animals, cushions organs/insulation/energy)

◦ Vitamins and minerals (required for chemical reactions)

2. Oxygen – required for chemical reactions to release energy in cells (provided by respiratory and cardiovascular systems)

3. Water – obtained by ingestion and lost by evaporation/excretion.

◦ Accounts for 60% to 80% of body weight and is the single most abundant chemical substance in the body.

◦ Provides environment needed for chemical reactions.

◦ Fluid base for secretions and excretions

4. Normal body temperature – 37 degrees Celsius and 98 degrees Fahrenheit

◦ If below, then metabolic reactions slow and eventually stop.

◦ If above, then metabolic reactions speed up to a pace that cannot be kept and body proteins lose shape and function

◦ Either extreme leads to death

5. Atmospheric pressure – force that air exerts on the body.

◦ Needs to remain stable for breathing/gas exchange in lungs.

◦ High altitudes have lower air pressure and gas exchange is too low to support cellular metabolism.

The ability of the body to keep its internal conditions in a dynamic state of equilibrium (balance) even though the outside world is continually changing.

Homeostasis is occurring when the body’s needs are met and it is functioning smoothly.

Almost every organ system plays a part in maintaining homeostasis.

Homeostasis

Examples:◦ Keeping adequate nutrient levels is difficult and

complicated.◦ Heart activity◦ Blood pressure◦ Removal of waste◦ Controlling body temperature

Keeping the body in equilibrium is difficult and complicated.

Communication is essential and is in the form of electrical impulses by the nervous system and hormones by the endocrine system.

All homeostatic control mechanisms have at least 3 interdependent components regardless of the variable being regulated.

1. Receptor is a sensor that responds to changes in the environment and sends the input to the control center via the afferent pathway.

2. control center determines the functioning range of the variable analyzes the input, and determines the appropriate response.

3. Effector is the output (response) to the stimulus that goes through the efferent pathway.

3 variables

1. Depresses the stimulus to shut off the whole control mechanism (negative feedback)

2. Enhances the stimulus to make the reaction occur at a faster rate (positive feedback)

Results of this response feedback to influence the stimulus

Most homeostatic control mechanisms Net effect is that the output of the system

shuts off the original stimulus or reduces its intensity.

The variable changes in a direction opposite (negative) to the initial change (it returns to the ideal value)

Examples:◦ Regulation of body temperature◦ Control of blood glucose levels with insulin and

glucose.

Negative Feedback

Rarely utilized because of the tendency to race out of control.

Net effect is to enhance or exaggerate the original stimulus so the activity (output) is accelerated

The variable changes in the same direction as the initial disturbance causing more deviation from the original value.

Controls infrequent events that do not need continuous adjustment.

Sets off a series of events that are self-perpetuating/explosive◦ Childbirth◦ Blood clotting.

Positive Feedback

Homeostatic imbalances disrupt the efficiency of organs and their control systems◦ Especially noticeable with increasing age◦ A cause of many diseases because usual negative

feedback mechanisms fail and are replaced by positive feedback mechanisms (heart failure)

Anatomical position is standing erect, feet together, arms at sides, thumbs pointed out, palms forward.

Every time a description is given it is assumed the body is in this position regardless of its actual position.

The Language of Anatomy

Allow proper explanations of body structures as they relate to one another.◦ The ears are lateral to the nose◦ The knee is distal to the thigh◦ The skin is superficial and fibula is deep to the

gastrocnemius

Directional Terms

1. Axial – head, neck, and trunk (the main axis of the body)

2. Appendicular – appendages/limbs attached to the main axis.

2 divisions of the body

1. Sagittal – vertical plane that divides the body into left and right sides (producing a sagittal section)

2. Frontal (coronal) – vertical plane that divides the body into anterior and posterior sides.

3. Transverse (horizontal) – horizontal plane that divides the body into inferior and superior parts ( producing a transverse or cross sections)

* And oblique section is a cut made diagonally between horizontal and vertical plans.

3 plains of the body

Superior (cranial) – toward the head, above Inferior (caudal) – away from the head, below Anterior ( ventral) – toward the front Posterior (dorsal) – toward the back Medial- toward the midline Lateral – away from the midline Intermediate – between a medial and lateral

structure Proximal – closer to the point of attachment Distal – away from the point of attachment Superficial – toward the body surface Deep – away from the body surface

Orientation and Directional Terms

Dorsal – protected by hard bony walls ◦ Cranial cavity encases the brain◦ Vertebral (spinal) cavity encloses the spinal cord

Body Cavaties

Ventral – contains internal organs (viscera)◦ Thoracic cavity is surrounded by the ribs and

chest muscles (including the diaphragm) Pleural cavities are lateral and each surrounds a lung Mediastinum

Pericardial cavity surrounds the heart Superior cavity surrounds other thoracic organs

( esophagus, trachea, etc)

Abdominopelvic cavity is inferior to the diaphragm and surrounded by muscle but not bone (except the dorsal backbone).1. Abdominal cavity contains the stomach,

intestines, spleen, liver, etc and is the most superior

2. Pelvic cavity contain the bladder, rectum, and reproductive organs and is the most inferior

Serous membrane (serosa) is thin but double-layered ◦ Parietal serosa covers the walls of the cavity◦ Visceral serosa covers the outer surfaces of the

organs (formed by the infolding of the parietal serosa)

Membranes in the Body Cavity

Serous membranes are named for the specific cavity and organ with which they are associated:◦ Parietal pericardium lines the pericardial cavity

and visceral pericardium covers the heart◦ Parietal pleura lines the pleural cavity and visceral

pleura covers the lung◦ Parietal peritoneum lines the abdominopelvic

cavity and visceral peritoneum covers those organs, etc.

1. Oral cavity is the mouth and contains teeth and tongue ( continuous with the rest of the digestive organs)

2. Nasal cavity is within (and posterior) to the nose and is a part of the respiratory system passageways.

3. Middle ear cavities are within the temporal bone of the skull just medial to the eardrum (contains the bones responsible for transmitting sound vibrations to the inner ear)

Other Body Cavities

4. Orbital cavities (orbits) contain the eyes and holds them in place.

5. Synovial (joint) cavities are fibrous capsules that surround freely-moving joints (elbow, knee, shoulder, etc.) filled with fluid to reduce friction between opposite bones.

Abdominopelvic cavity is divided into 9 regions using 2 transverse and 2 parasagittal planes ( a tic-tac-toe grid) centered over the naval (easiest to start there)

Umbilical region starts around the naval (1) Left and right lumbar regions immediately lateral

(2 and 3) Epigastric (“above stomach”) region is superior to

umbilical (4) Left and right hypochondriac (“below-cartilage”

refers to being deep to rib cartilage) regions immediately lateral (5 and 6)

Hypogastric (“below-stomach”) region is inferior to umbilical. (7)

Left and right iliac (superior part of hip) regions immediately lateral (8 and 9)