chapter 6

The Human Body

Introduction

• A working knowledge of anatomy is essential.
• Terminology:
  • Anatomy: The study of the body's structure.
  • Physiology: The study of the body's functions.
  • Pathophysiology: The study of how disease affects the body's functions.

Topographic Anatomy

• Applies to a body in the anatomic position:
  • Patient stands facing you, arms at the side, palms forward.

Planes of the Body

• Imaginary straight lines that divide the body.
• Three main planes:
  • Coronal (frontal) plane: Divides the body into front and back sections.
  • Sagittal (lateral) plane: Divides the body into left and right sections.
  • Midsagittal (midline) plane: Divides the body into equal left and right halves.
  • Transverse (axial) plane: Divides the body into top and bottom sections.

Cells to Systems

• Cells: The foundation of the human body.
• Tissues: Cells that share a common function.
• Organs: Groups of tissues that perform similar or interrelated functions.
• Body systems: Organs with similar functions working together.

The Skeletal System: Anatomy

• The skeleton provides our recognizable human form.
• Composed of 206 bones.
• Divided into:
  • Axial skeleton
  • Appendicular skeleton
  • Pelvis

The Axial Skeleton

• Foundation to which the arms and legs are attached.
• Includes:
  • Skull
  • Facial bones
  • Thoracic cage
  • Vertebral column

Joints

• Occur wherever bones come in contact.
• Consist of the ends of bones and connecting/supporting tissues.
• Two types:
  • Ball-and-socket joint: Allows rotation and bending (e.g., shoulder).
  • Hinge joint: Motion restricted to flexion and extension (e.g., elbow).

Skull

• Cranium: Made up of 4 bones.
• Face: Made up of 14 bones.

Spinal Column

• Composed of 33 bones (vertebrae).
• Divided into 5 sections:
  • Cervical
  • Thoracic
  • Lumbar
  • Sacrum
  • Coccyx

Thorax

• Formed by 12 thoracic vertebrae and 12 pairs of ribs.
• Thoracic cavity contains:
  • Heart
  • Lungs
  • Esophagus
  • Great vessels

The Appendicular Skeleton

• Arms, legs, their connection points, and the pelvis.
• Includes:
  • Joints
  • Upper extremities
  • Pelvis
  • Lower extremities

Upper Extremities

• Extend from the pectoral girdle to the fingertips.
• Composed of arms, forearms, hands, and fingers.
• Shoulder girdle: Three bones come together:
  • Clavicle
  • Scapula
  • Humerus
• Arm:
  • The humerus is the supporting bone.
• Forearm:
  • Consists of the radius and ulna.
  • Radius is on the lateral side.
  • Ulna is on the medial side.
• Wrist and hand:
  • Ball-and-socket joint.
  • Principal bones: Carpals, metacarpals, phalanges.

The Pelvis

• The pelvic girdle consists of:
  • Two coxae (hip bones).
  • Sacrum
  • Coccyx
• Each pelvic bone is formed by the fusion of the ilium, ischium, and pubis.
• Posteriorly, the ilium, ischium, and pubis bones are joined by the sacrum.
• Anteriorly, the pubic symphysis is where the right and left pubic bones are joined.

Lower Extremities

• Femur:
  • Longest bone in the body.
  • Connects into the acetabulum (pelvic girdle) via a ball-and-socket joint.
  • The greater and lesser trochanters are where the major muscles of the thigh connect to the femur.
• Knee: Connects the upper leg to the lower leg.
  • Kneecap (patella).
• Lower leg:
  • Tibia (shinbone) on the anterior side of the leg.
  • Fibula on the lateral side of the leg.
• Ankle:
  • A hinge joint that allows flexion/extension of the foot.
• Foot:
  • Contains 7 tarsal bones.
  • 5 metatarsal bones form the substance of the foot.
  • Toes are formed by phalanges.

The Skeletal System: Physiology

• Gives the body its shape.
• Protects fragile organs.
• Allows for movement.
• Stores calcium.
• Helps create blood cells.

The Musculoskeletal System: Anatomy

• Provides:
  • Form
  • Upright posture
  • Movement
  • Protection of vital internal organs
• Types of muscles:
  • Skeletal (voluntary) muscle
  • Smooth muscle
  • Cardiac muscle

The Musculoskeletal System: Physiology

• Contraction and relaxation of the system make it possible to move and manipulate the environment.
• A by-product of this movement is heat.
• Muscles also protect the structures under them.

The Respiratory System: Anatomy

• Structures of the body that contribute to respiration (the process of breathing).

Upper Airway

• Includes:
  • Nose
  • Mouth (oral cavity)
  • Tongue
  • Jaw (mandible)
  • Larynx (divides upper and lower airway)
  • Pharynx (Nasopharynx, Oropharynx, Laryngopharynx)
  • Trachea
  • Epiglottis

Lower Airway

• Thyroid cartilage (Adam's apple).
• Cricoid cartilage: Immediately below the thyroid cartilage.
• Cricothyroid membrane.
• Trachea ends at the carina, dividing into right and left bronchi leading to bronchioles.

Lungs

• The two lungs are held in place by:
  • Trachea
  • Arteries and veins
  • Pulmonary ligaments
• Divided into lobes:
  • Right lung has upper, middle, and lower lobes.
  • Left lung has upper and lower lobes.
• Within the lobes are bronchi, bronchioles, and alveoli which allow for gas exchange.
• Pleura: A layer of smooth, glistening tissue that covers each lung and lines the chest cavity.
• Between the two layers is a small amount of fluid that allows the tissues to glide smoothly.

Muscles of Breathing

• Diaphragm is the primary muscle of breathing.
• Also involved are:
  • Neck (cervical muscles)
  • Intercostal muscles
  • Abdominal muscles
  • Pectoral muscles

Inhalation

• Diaphragm and intercostal muscles contract.
• Pressure in the thoracic cavity decreases.
• Lungs fill with air.
• Active part of the respiratory cycle.

Exhalation

• Diaphragm and intercostal muscles relax.
• Thoracic cavity returns to its normal shape and volume.
• Passive portion of the respiratory cycle.

The Respiratory System: Physiology

• Function is to provide the body with oxygen and eliminate carbon dioxide.

• Ventilation and respiration are two separate, interdependent functions.

• Respiration is the exchange of oxygen and carbon dioxide in the alveoli and tissues.

  • Provides oxygen to the cells and removes waste carbon dioxide.
  • Diffusion: A passive process in which molecules move from an area of higher concentration to an area of lower concentration.

• Chemical control of breathing:

  • The brainstem controls breathing by monitoring carbon dioxide in the blood and spinal fluid.
  • The primary reason for breathing is to lower carbon dioxide levels.
  • Hypoxic drive.

• Nervous system control of breathing:

  • The medulla initiates ventilation cycles, stimulated by high carbon dioxide levels.
  • The pons has two areas that help augment respirations during emotional or physical stress.

• Ventilation is simple air movement into and out of the lungs; requires chest rise and fall.

  • Tidal volume: The amount of air moved into or out of the lungs during a single breath.
  • Residual volume: The gas that remains in the lungs to keep the lungs open.

• Dead space: The portion of the respiratory system that has no alveoli and where little or no exchange of gas between air and blood occurs.

• Respiratory \ rate \times tidal \ volume = minute \ volume

Characteristics of Normal Breathing

• Normal rate and depth (tidal volume).
• Regular rhythm or pattern of inhalation and exhalation.
• Clear, audible breath sounds on both sides of the chest.
• Regular rise and fall movement on both sides of the chest.
• Movement of the abdomen.

Inadequate Breathing Patterns in Adults

• Labored breathing
• Muscle retractions
• Pale, cyanotic, cool, damp skin
• Tripod position
• Agonal gasps

The Circulatory System: Anatomy

• Complex arrangement of connected tubes (arteries, arterioles, capillaries, venules, and veins).
• Two circuits:
  • Systemic circulation (body)
  • Pulmonary circulation (lungs)

The Heart

• Hollow muscular organ made of specialized cardiac muscle.

• Works as two paired pumps, each divided into:

  • Atrium (upper chamber)
  • Ventricle (lower chamber)

• Circulation:

  • The heart receives its blood from the aorta.
  • The right side receives deoxygenated blood from the veins.
  • The left side receives oxygenated blood from the lungs.

• Normal resting heart rate (HR) is 60–100 beats/min.

• Stroke volume (SV): Amount of blood moved by one beat.

• Cardiac output (CO): Amount of blood moved in 1 minute.

• HR \times SV = CO

• Electrical conduction system:

  • Specialized tissue capable of initiating and conducting electrical current.
  • Causes smooth, coordinated contractions.
  • Contractions produce pumping action.

Arteries

• Carry blood from the heart to all body tissues.
• The aorta branches into:
  • Coronary arteries.
  • Carotid arteries.
  • Hepatic arteries.
  • Renal arteries.
  • Mesenteric arteries.
• Pulmonary artery: Carries oxygen-poor blood to the lungs.
• Arteries branch into smaller arteries and then into arterioles.
• Arterioles branch into a series of increasingly smaller vessels until they connect to the capillaries.
• Pulse:
  • Palpated most easily at the neck, wrist, or groin.
  • Created by forceful pumping of blood out of the left ventricle and into the major arteries.

Capillaries

• Connect arterioles to venules.
• Fine end divisions of the arterial system.
• Allow contact between blood and cells.

Veins

• Return oxygen-depleted blood to the heart.
• The superior vena cava carries blood returning from the head, neck, shoulders, and upper extremities.
• The inferior vena cava carries blood from the abdomen, pelvis, and lower extremities.
• Join at the right atrium.

The Spleen

• Solid organ located under the rib cage.
• Filters blood.
• Particularly susceptible to injury from blunt trauma.

Blood Composition

• Plasma (liquid).
• Red blood cells (erythrocytes).
• White blood cells (leukocytes).
• Platelets.

The Circulatory System: Physiology

• Blood pressure: Pressure that blood exerts against the walls of arteries.
  • Systole: When the left ventricle of the heart contracts, it pumps blood from the ventricle into the aorta.
  • Diastole: When the muscle of the ventricle relaxes, the ventricle fills with blood.
• Blood pressure readings:
  • Systolic blood pressure: High point of wave.
  • Diastolic blood pressure: Low point of wave.

Normal Circulation in Adults

• Automatically adjusted and controlled.
• Perfusion: Circulation of blood in an organ or tissue in adequate amounts to meet the needs of the cells.
• Hypoperfusion: Inadequate blood supply to organs, tissues, and cells.

Inadequate Circulation in Adults

• The system can adjust to small blood loss:
  • Vessels constrict.
  • The heart pumps more rapidly.
• With a large loss, adjustment fails, and the patient goes into shock.
• Mean arterial pressure can help detect shock.

Functions of Blood

• Fighting infection
• Transporting oxygen
• Transporting carbon dioxide
• Controlling pH
• Transporting wastes and nutrients
• Clotting (coagulation)

Nervous System Control of the Cardiovascular System

• The sympathetic nervous system is responsible for the fight-or-flight response.
  • Sends commands to adrenal glands.
  • Epinephrine (adrenaline) and norepinephrine (noradrenaline) are secreted to stimulate the heart and blood vessels.
• Blood vessels have alpha-adrenergic receptors.
• The heart and lungs have beta-adrenergic receptors.
• Baroreceptors sense pressure in the blood vessels.
• The sympathetic and parasympathetic nervous system balance each other.

The Nervous System: Anatomy and Physiology

• The nervous system is perhaps the most complex organ in the body.
• Divided into two main portions:
  • Central nervous system (CNS)
  • Peripheral nervous system

Central Nervous System

• Brain: Controlling organ of the body.
  • Subdivisions: Cerebrum, Cerebellum, Brainstem.
• Cerebrospinal fluid:
  • Cushions and protects the brain and spinal cord.
• Circulation in the head:
  • Oxygenated blood is supplied via carotid arteries.
  • Deoxygenated blood is drained by the internal and external jugular veins.
• Spinal cord:
  • Extension of the brainstem.
  • Transmits messages between the brain and body.

Peripheral Nervous System

• Divided into two main portions:
  • Somatic nervous system
  • Autonomic nervous system
• Somatic nervous system:
  • Transmits signals from the brain to voluntary muscles.
• Autonomic nervous system:
  • Involuntary actions.
  • Split into two areas: Sympathetic nervous system (fight-or-flight), Parasympathetic nervous system (slows body).
• Two types of nerves within the peripheral nervous system:
  • Sensory nerves carry information from the body to the CNS.
  • Motor nerves carry information from the CNS to muscles.

The Integumentary System (Skin): Anatomy

• Two layers:
  • Epidermis (superficial)
  • Dermis (deeper)
• Subcutaneous tissue lies beneath the skin (fat that insulates and serves as an energy reservoir).

The Integumentary System (Skin): Physiology

• The skin is the largest single organ in the body.
• Three major functions:
  • Protects the body in the environment.
  • Regulates body temperature.
  • Transmits information from the environment to the brain.

The Digestive System: Anatomy

• Gastrointestinal system.
• Abdomen: The second major body cavity.
  • Contains major organs of digestion and excretion.
  • Organized into 4 quadrants: Right upper, Left upper, Right lower, Left lower.
• Mouth: Lips, cheeks, gums, teeth, tongue.
• Salivary glands
• Oropharynx
• Esophagus
• Stomach
• Pancreas
• Liver
• Bile ducts
• Small intestine
• Large intestine
• Appendix
• Rectum

The Digestive System: Physiology

• Enzymes are added to food by:
  • Salivary glands, stomach, liver, pancreas, and small intestine.
• Food is converted into basic sugars, fatty acids, and amino acids.
• Further processed by the liver and circulated via blood throughout the body.

The Lymphatic System

• Elements of the lymphatic system:
  • Spleen
  • Lymph nodes
  • Lymph
  • Lymph vessels
  • Thymus gland
  • Other components
• Supports the circulatory system and immune system.
• Lymph is a thin, straw-colored fluid that carries oxygen and nutrients to cells and waste products away; helps rid the body of toxins and other harmful materials.

The Endocrine System: Anatomy and Physiology

• Complex message and control system.
• Integrates many body functions.
• Hormones are released directly into the bloodstream (Epinephrine, norepinephrine, insulin).
• The brain controls the release of hormones.
• Excesses or deficiencies in hormones can cause disease.

The Urinary System: Anatomy and Physiology

• Controls the discharge of certain waste materials filtered from the blood by the kidneys.
• Controls fluid balance in the body.
• Filters and eliminates wastes.
• Controls pH balance.
• Components: Kidneys, Ureter, Urinary bladder.

The Genital System: Anatomy and Physiology

• Controls reproductive processes.

Male System

• Consists of:
  • Testicles
  • Epididymis
  • Vasa deferentia
  • Prostate gland
  • Seminal vesicles
  • Penis

Female System

• Consists of:
  • Ovaries
  • Fallopian tubes
  • Uterus
  • Cervix
  • Vagina

Life Support Chain

• All cells in the body require oxygen, nutrients, and waste removal.
• The circulatory system is the carrier of these supplies and wastes.
• If interference occurs, cells become damaged and die.
• Cells use oxygen to turn nutrients into chemical energy through metabolism.
• Aerobic metabolism uses oxygen.
• Cells switch to anaerobic metabolism when oxygen is limited.
• Movement of oxygen, waste, and nutrients occurs by diffusion.
• pH is critical to diffusion; the body expends a large amount of energy to maintain normal pH.

Pathophysiology

• The study of functional changes that occur when the body reacts to a disease.
• Respiratory compromise is the inability of the body to move gas effectively (Hypoxia, Hypercarbia).

Factors That Impair Ventilation

• Blocked airway
• Impairment of the muscles of breathing
• Airway obstructed physiologically (asthma)
• Other factors

Factors That Impair Respiration

• Change in atmosphere (High altitudes).
• Impaired movement of the gas across the cell membrane.
• V/Q ratio: How much gas is being moved effectively through the lungs vs how much blood is flowing around the alveoli where perfusion occurs; a mismatch occurs when one variable is abnormal.

Effects of Respiratory Compromise on the Body

• Oxygen levels fall and carbon dioxide levels rise.
• Respiratory rate increases.
• Blood becomes more acidic.
• The brain sends commands to the body to breathe.
• Cells move from aerobic to anaerobic metabolism.

Shock

• Occurs when organs and tissues do not receive enough oxygen; impaired oxygen delivery causes cellular hypoxia.
• Categorized into several types depending on the cause.

Effects of Shock on the Body

• The level of oxygen supplied to the tissues falls.
• Cells engage in anaerobic metabolism.
• Severe metabolic acidosis ensues.
• Baroreceptors initiate the release of epinephrine and norepinephrine.
• The heart rate increases.
• Interstitial fluid moves into the capillaries.

Impairment of Cellular Metabolism

• Results in the inability to properly use oxygen and glucose at the cellular level.
• Cells create energy through anaerobic metabolism, which can result in metabolic acidosis.
• Brain cells cannot use alternative fuels.
• Cellular injury may become irreversible.