Anatomy and Physiology: Subspecialties

Anatomy and Physiology

• Anatomy and physiology are the branches of science that study the body's parts and their functions, respectively.
• Anatomy was initially studied through dissection and now uses imaging techniques.
• Physiology studies the functions of the body.

Subspecialties of Anatomy

• Embryology studies the first eight weeks of development after egg fertilization.
• Developmental biology studies the complete development from fertilization to death.
• Cell biology focuses on cellular structure and functions.
• Histology studies the microscopic structure of tissues.
• Surface anatomy examines surface markings to understand internal anatomy through visualization and palpation.
• Gross anatomy studies structures that can be examined without a microscope.
• Systemic anatomy focuses on the structure of specific systems (e.g., nervous or respiratory).
• Regional anatomy studies specific regions of the body (e.g., head or chest).
• Radiographic anatomy studies body structures visualized with x-rays.
• Pathological anatomy studies structural changes associated with disease.

Subspecialties of Physiology

• Neurophysiology studies the functional properties of nerve cells.
• Endocrinology studies hormones and their control of body functions.
• Cardiovascular physiology studies the functions of the heart and blood vessels.
• Immunology studies the body's defense against disease-causing agents.
• Respiratory physiology studies the functions of air passageways and lungs.
• Renal physiology studies the functions of the kidneys.
• Exercise physiology studies changes in cell and organ functions due to muscular activity.
• Pathophysiology studies functional changes associated with disease and aging.

Structure and Function

• Structure and function are closely related in the body.
• The structure of a body part enables it to perform certain functions.
• Bone structure protects the brain.
• Thin air sacs in the lungs enable oxygen movement.

Levels of Structural Organization

• The body has six levels of organization.
• These levels include chemical, cellular, tissue, organ, system, and organismal.

Chemical Level

• Atoms, like carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), calcium (Ca), and sulfur, are the smallest units of matter.
• Molecules are formed when two or more atoms join together, such as deoxyribonucleic acid (DNA) and glucose.

Cellular Level

• Molecules combine to form cells.
• Cells are the basic structural and functional units of an organism.
• The body contains many kinds of cells, including muscle, nerve, and epithelial cells.

Tissue Level

• Tissues are groups of cells and surrounding materials.
• There are four basic types of tissues: epithelial, connective, muscular, and nervous.

Organ Level

• Tissues join together to form organs.
• Organs are composed of two or more different tissue types.
• Organs have specific functions and recognizable shapes, such as the heart, lungs, and kidneys.
• The stomach, for example, includes serous membrane, smooth muscle, and epithelial layers for digestion.

System Level

• A system consists of related organs with a common function, such as the digestive system.
• Organs within the digestive system include the mouth, small and large intestines, liver, gallbladder, and pancreas.
• The human body has eleven systems.

Organismal Level

• An organism is any living individual.
• All parts of the body function together in an organism.

Noninvasive Diagnostic Techniques

• Used to assess aspects of body structure and function.
• Inspection involves observing the body for any changes.
• Palpation involves gently touching body surfaces with hands.
• Auscultation involves listening to body sounds (e.g., with a stethoscope).
• Percussion involves tapping on the body surface with fingertips and listening to echoes.

Basic Life Processes

• Distinguish living from non-living things.
• Six important life processes: metabolism, responsiveness, movement, growth, differentiation, reproduction.

Metabolism and Responsiveness

• Metabolism is the sum of all chemical processes in the body.
• Catabolism breaks down complex chemical substances into simpler components.
• Anabolism builds up complex chemical substances from smaller components.
• Responsiveness is the body's ability to detect and respond to changes, such as a decrease in body temperature or responding to sound.
• Nerves (electrical signals) and muscle cells (contracting) are involved in responsiveness.

Movement and Growth

• Movement is the motion of the whole body, its organs, cells, and tiny subcellular structures.
• Leg muscles move the body.
• Growth is an increase in body size due to an increase in existing cells, the number of cells, or both.
• Bone growth involves an increase in materials between cells.

Differentiation and Reproduction

• Differentiation is the development of a cell from an unspecialized to a specialized state.
• Cells develop specialized structures and functions.
• Stem cells give rise to cells that undergo differentiation.
• Reproduction deals with forming new cells (growth, repair, or replacement).
• Reproduction also deals with the production of a new individual.

Autopsy (Postmortem examination)

• A postmortem examination of the body and internal organs.
• It identifies the cause of death.
• It identifies diseases not detected during life.
• It determines the extent of injuries and their contribution to death.
• It detects hereditary conditions.

Homeostasis

• Equilibrium (balance) in the body’s internal environment.
• It is a dynamic condition that needs a narrow range to maintain life.
• The endocrine and nervous system (either working together or independently) are involved in it.
• Maintaining blood glucose levels ranging between 70 and 110 mg of glucose/dL of blood is an example of homeostasis.
• The whole body contributes to maintain the internal environment within normal limits.

Homeostasis and Body Fluids

• Maintaining the volume and composition of body fluids is important.
• Body fluids are dilute, watery solutions containing dissolved chemicals inside or outside of cells.
• Intracellular fluid (ICF) is fluid within cells.
• Extracellular fluid (ECF) is fluid outside cells.
• Interstitial fluid is ECF between cells and tissues.

ECF and Body Location

• Blood plasma is ECF within blood vessels.
• Lymph is ECF within lymphatic vessels.
• Cerebrospinal fluid (CSF) is ECF in the brain and spinal cord.
• Synovial fluid is ECF in synovial joints.
• Aqueous humor and vitreous body are ECF in eyes.

Interstitial Fluid and Body Function

• Cellular function depends on the regulation of the composition of interstitial fluid.
• The body’s internal environment is important.
• The composition of interstitial fluid changes as it moves.
• Movement back and forth across capillary walls provides nutrients (glucose, oxygen, ions) to tissue cells and removes waste (carbon dioxide).

Control of Homeostasis

• Stress is anything that causes an imbalance in the internal environment.
• Homeostasis is constantly being disrupted.
• Physical insults, such as intense heat or lack of oxygen, disrupts homeostasis.
• Changes in the internal environment such as a drop in blood glucose due to lack of food, disrupts homeostasis.
• Physiological stress, such as demands of work or school, disrupts homeostasis.
• Disruptions can be mild and temporary (balance is quickly restored).
• Disruptions can also be intense and prolonged (poisoning or severe infections).

Feedback System

• This is a cycle of events in which the body is monitored, evaluated, changed, and re-monitored in a feedback loop.
• Each monitored variable is called a controlled condition (e.g., blood glucose levels, blood pressure, body temperature).
• Any disruption to the controlled condition is termed a stimulus.
• The three basic components are the receptor (detector), control center, and effector.

Feedback Systems: Receptor

• Body structure that monitors changes in a controlled condition.
• It sends input to the control center, such as a nerve ending of the skin responding to temperature change.
• Receptors are part of an afferent pathway as the information flows towards the control centre.

Feedback Systems: Control Center

• The brain acts as a control center.
• Sets the range of values to be maintained.
• Evaluates input received from receptors and generates output command.
• Nerve impulses and hormones are factors here.
• Brains acts as a control center receiving nerve impulses from skin temperature receptors.

Feedback Systems: Effector

• Receives output from the control center.
• Produces a response or effect that changes the controlled condition.
• It is found in nearly every organ or tissue.
• Example: body temperature drops > the brain sends and impulse to the skeletal muscles to contract > shivering to generate heat.

Negative and Positive Feedback Systems

• Negative feedback systems reverse a change in a controlled condition.
• An example of Negative feedback systems is the regulation of blood pressure.
• Positive feedback systems strengthen or reinforce a change in one of the body’s-controlled conditions.
• Natural childbirth is an example of positive feedback loops.

Negative Feedback: Regulation of Blood Pressure (BP)

• Regulation of BP follows a Negative feedback loop.
• External or internal stimulus can increase BP.
• Increased BP is detected by Baroreceptors (pressure sensitive receptors).
• Baroreceptors send nerve impulses to the brain for interpretation.
• A response is sent via nerve impulses to the heart and blood vessels.
• This negative feedback loop causes: BP drops and homeostasis is restored / Drop in BP negates the original stimulus.

Positive Feedback Systems: Natural Childbirth

• Uterine contractions cause the vagina to open.
• Stretch-sensitive receptors in the cervix send an impulse to the brain.
• Oxytocin is released into the blood.
• Contractions are enhanced and the baby pushes farther down the uterus.
• The cycle continues to the birth of the baby (no stretching).

Positive Feedback: Blood Loss

• In normal conditions, the heart pumps blood under pressure to body cells (oxygen and nutrients).
• In severe blood loss: blood pressure drops, cells receive less oxygen and function less efficiently.
• If blood loss continues: heart cells become weaker, heart doesn’t pump, BP continues to fall due to less oxygen in the circulatory structure.

Homeostatic Imbalances

• Occur when the normal equilibrium of body processes is disrupted.
• In moderate imbalance: there is a disorder or abnormality of structure and function + disease/symptoms + objective changes (fever or swelling)+ subjective changes such as headache
• In severe imbalance: death

Basic Anatomical Terminology

• A common language referring to body structures and their functions.
• Anatomists use standard anatomical position and special vocabulary in relating body parts.

Body Positions

• Descriptions of the human body assume a specific stance.
• Anatomical position: body upright, standing erect facing the observer, head and eyes facing forward, feet are flat on the floor and forward, upper limbs to the sides, and palms turned forward.
• Prone position: body is lying face down.
• Supine position: body is lying face up.

Regional Names

• Several major regions of the human body's structure: most principal regions, head (skull and face), neck (supports the head and attaches to trunk), trunk (chest, abdomen, and pelvis), upper limbs (attaches to trunk (shoulder, armpit, and arm), lower limbs (attaches to trunk (buttock, thigh, leg, ankle, and foot).

Directional Terms

• Describe the position of one body part relative to another.
• They come in pairs with opposite meanings (e.g., anterior (front) and posterior (back)).
• They only make sense when used to describe the position of one structure relative to another.
• For example, the esophagus is posterior to the trachea, and the knee is superior to the ankle.
• Anterior = Nearer to the front of the body
• Posterior = Nearer to the back of the body
• Proximal = Nearer to the attachment of a limb to the trunk or near to the origin of a structure
• Distal = Further from the attachment of a limb to the trunk or further from the origin of a structure
• Lateral = Further from the midline
• Medial = Nearer to the midline
• Superior = Toward the head
• Inferior = Away from the head

Planes and Sections

• Imaginary flat surfaces that pass through the body parts
• Sagittal plane: divides the body into right and left sides
• Midsagittal plane: divides the body into equal right and left sides
• Parasagittal plane: divides the body into unequal right and left sides
• Frontal or coronal plane: divides the body or an organ into anterior (front) and posterior (back) portions
• Transverse plane: divides the body or an organ into superior (upper) and inferior (lower) portions; also called cross-sectional or horizontal plane
• Oblique plane: passes through the body or an organ at an angle: between transverse and sagittal plane, or Between transverse and frontal plane
• Section: cut of the body made along a plane

Body Cavities

• Spaces within the body to protect, separate, and support internal organs
• Cranial cavity: contains cranial bones; protects the brain
• Thoracic cavity
• Abdominopelvic cavity

Cranial Cavity and Vertebral Canal

• Cranial cavity: formed by the cranial bones; protects the brain
• Vertebral canal: formed by bones of vertebral column; contains the spinal cord
• Meninges: layers of protective tissue that line the cranial cavity and vertebral canal

Thoracic Cavity

• Also called the chest cavity
• Formed by:
  • Ribs
  • Muscles of the chest
  • Sternum (breastbone)
  • Vertebral column (thoracic portion)
• Within the thoracic cavity:
  • Pericardial cavity: fluid-filled space that surround the heart
  • Pleural cavity: two fluid-filled spaces that surround each lung
• Mediastinum: central part of the thoracic cavity (between lungs; extending from the sternum to the vertebral column; first rib to the diaphragm)
  • Diaphragm: dome-shaped muscle that separates the thoracic cavity from the abdominopelvic cavity

Abdominopelvic Cavity

• Extends from the diaphragm to the groin
• Encircled by the abdominal wall and bones and muscles of the pelvis
  • Abdominal cavity: stomach, spleen, liver, gallbladder, small and large intestines
  • Pelvic cavity: urinary bladder, internal organs of reproductive system, and portions of the large intestine

Thoracic and Abdominal Cavity Membranes

• Viscera: organs of the thoracic and abdominal pelvic cavities
  • Serous membrane: A thin, slippery membrane that covers the viscera
  • Parietal layer: Lines the wall of the cavities
  • Visceral layer: Covers the viscera within the cavities
• Special kinds of serous membranes:
  • Pleura: Serous membrane of the pleural cavities / Visceral pleura clings to surface of lungs / Parietal pleura lines the chest wall
  • Pericardium: Serous membrane of the pericardial cavity Visceral pericardium covers the heart /Parietal pericardium lines the chest wall
  • Peritoneum: Serous membrane of the abdominal cavity / Visceral peritoneum covers the abdominal cavity /Parietal peritoneum lines the abdominal wall

Other Body Cavities

• Oral (mouth) cavity: tongue and teeth
• Nasal cavity: nose
• Orbital cavities: eyeball
• Middle ear cavities: small bones of the middle ear
• Synovial cavities: joints

Abdominopelvic Regions

• Tic-Tac-Toe grid divides the cavity as such: two horizontal and two vertical lines, subcostal line (top horizontal, inferior to rib cage), transtubercular line (bottom horizontal; inferior to top of the hip bone), midclavicular lines (two vertical lines); midpoints to clavicles and medial to the nipples
• Nine abdominopelvic regions: Right and left hypochondriac / Epigastric and hypogastric (pubic) / Right and left lumbar / Right and left inguinal (iliac / Umbilical

Abdominopelvic Regions

• Based on the vertical and horizontal lines that pass through the umbilicus.
• Right upper quadrant (RUQ), Left upper quadrant (LUQ), Right lower quadrant (RLQ) and Left lower quadrants (LLQ).