Physiology Flow Pathways and Structures

Flow of Units That Need It

• Digestive Flow:
    - Pathway:
      - Mouth
      - Pharynx
      - Esophagus
      - Stomach
      - Duodenum
      - Jejunum
      - Ileum
      - Cecum
      - Ascending Colon
      - Transverse Colon
      - Descending Colon
      - Sigmoid Colon
      - Rectum
      - Anal Canal
    - Food Movement Mechanics:
      - Peristalsis:
        - Description: A series of wave-like muscle contractions that moves food through the digestive tract. It pushes contents forward.
      - Segmentation:
        - Description: Rhythmic contractions of non-adjacent segments of the intestine, mixing the food contents and enhancing absorption.

• Respiratory Airflow:
    - Pathway:
      - Nares (nostrils)
      - Nasal Cavity / Conchae
      - Pharynx
      - Larynx
      - Trachea
      - Primary Bronchi
      - Secondary Bronchi
      - Tertiary Bronchi
      - Bronchioles
      - Terminal Bronchioles
      - Respiratory Bronchioles
      - Alveolar Ducts
      - Alveoli

• Lymph Flow:
    - Pathway:
      - Interstitial Fluid
      - Lymphatic Capillaries
      - Lymphatic Vessels
      - Lymph Nodes
      - Lymphatic Trunks
      - Collecting Ducts
      - Venous Circulation
    - Important:
      - Thoracic Duct starts from the cisterna chyli.

• Nephron / Urinary Flow:
    - Pathway:
      - Afferent Arteriole
      - Glomerulus
      - Bowman's Capsule
      - Proximal Convoluted Tubule
      - Loop of Henle
      - Distal Convoluted Tubule
      - Collecting Duct
    - Then Urine Flow:
      - Collecting Duct
      - Papillary Duct
      - Minor Calyx
      - Major Calyx
      - Renal Pelvis
      - Ureter
      - Urinary Bladder
      - Urethra

Blood Flow Through Heart

• Full Blood Flow:
    - Cycle Pathway:
        - Body → Superior & Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle
        - Right Ventricle → Pulmonary Semilunar Valve → Pulmonary Trunk → Pulmonary Arteries → Lungs →
        - Lungs → Pulmonary Veins → Left Atrium → Mitral (Bicuspid) Valve → Left Ventricle
        - Left Ventricle → Aortic Semilunar Valve → Aorta → Body

• Flow Breakdown:
    1. Body → Right Heart:
       - Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle
    2. Right Heart → Lungs:
       - Pulmonary Valve → Pulmonary Arteries → Lungs
    3. Lungs → Left Heart → Body:
       - Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta

Sound Conduction Flow

• Pathway:
    - Tympanic Membrane → Malleus → Incus → Stapes → Oval Window → Cochlear Fluid → Organ of Corti

Visual Pathway Basics in Eye

• Not a full neural pathway, but key locations known:
    - Light Focused onto Retina
    - Best Visual Acuity: Fovea Centralis
    - Optic Nerve Exits at Optic Disc

Structure -> Function for Each Unit

Nervous System:

• Spinal Cord / Pathways / ANS / Special Senses
    - Spinal Cord Gray Horns:
      - Posterior (Dorsal) Horn:
        - Function: Receives sensory information
      - Anterior (Ventral) Horn:
        - Function: Contains cell bodies of motor neurons
      - Lateral Horn:
        - Function: Contains autonomic neuron cell bodies in some regions

• Roots:
      - Dorsal Root:
        - Function: Sensory fibers entering the cord
      - Ventral Root:
        - Function: Motor fibers leaving the cord

• White Matter Tracts:
    - Ascending Tracts:
      - Function: Carry sensory information to the brain
    - Descending Tracts:
      - Function: Carry motor commands from the brain
    - Spinothalamic Tract:
      - Carries pain, temperature, and crude touch; classified as an ascending sensory tract.
    - Dorsal Column Pathway:
      - Function: Carries fine touch, vibration, and proprioception.

• Extent of Spinal Cord:
    - Extends from foramen magnum to approximately L1-L2 vertebrae.

• Sympathetic Division:
    - Description: Associated with 'Fight or Flight' response; increases heart rate, mobilizes energy, prepares the body for emergency situations.

• Parasympathetic Division:
    - Description: Associated with 'Rest and Digest' response; conserves energy and supports digestive functions.

Eye Structures

• Optic Disc:
    - Function: Where vessels and nerve fibers leave the retina; commonly referred to as the blind spot.
• Macula:
    - Description: Area responsible for central vision.
• Fovea Centralis:
    - Description: Area of the retina with the greatest visual acuity and the highest density of cone cells.
• Choroid:
    - Description: Vascular pigmented layer that nourishes the retina.

Ear Structures

• Tympanic Membrane:
    - Description: Vibrates in response to sound waves.
• Ossicles:
    - Description: Amplify sound, consisting of the malleus, incus, and stapes.
• Oval Window:
    - Function: Transmits vibrations into the inner ear fluid.
• Organ of Corti:
    - Description: Contains sensory receptors responsible for hearing.
• Tectorial Membrane:
    - Function: Interacts with hair cells to facilitate sound transduction.

Endocrine System

• Endocrine Gland:
    - Definition: Glands that release hormones directly into the blood, targeting specific cells with receptors.
• Exocrine Gland:
    - Definition: Glands that release secretions through ducts.
• Hypothalamus:
    - Description: Integrates nervous and endocrine systems; controls the pituitary gland.
• Pituitary Gland:
    - Description: Major endocrine control gland; responds to signals from the hypothalamus.
• Thyroid Gland:
    - Function: Produces thyroxine (T4) and triiodothyronine (T3), regulating metabolism.
• Parathyroid Glands:
    - Function: Produce parathyroid hormone (PTH) which increases blood calcium levels.
• Pineal Gland:
    - Function: Produces melatonin; regulates circadian rhythms.
• Thymus:
    - Description: Has an endocrine function, particularly in immune system development.
• Pancreas:
    - Endocrine Part: Islets release insulin and glucagon.
    - Exocrine Part: Acini release digestive enzymes.

Lymphatic / Immune System

• Lymph Nodes:
    - Function: Filter lymphatic fluid and house immune cells.
• Tonsils / Adenoids:
    - Description: Monitor pathogens that enter through the nose and mouth.
• Appendix:
    - Description: Lymphoid tissue that plays a role in immune responses.
• Thoracic Duct:
    - Function: Returns lymph to venous circulation; begins at the cisterna chyli.
• Lymphatic Capillaries:
    - Function: Collect excess interstitial fluid.
• Spleen:
    - Function: Filters blood (not lymph); removes old red blood cells and stores immune cells.

Respiratory System

• Conchae:
    - Function: Warm, humidify, and filter incoming air; increase turbulence.

• Pharynx:
    - Function: Passageway for both air and food.

• Larynx:
    - Function: Maintains airway, allows sound production, and protects the lower airway.

• Trachea:
    - Function: Conducting passage supported by cartilaginous rings.

• Bronchi:
    - Function: Conduct air; supported by cartilaginous structures.

• Bronchioles:
    - Function: Conduct air; not supported by cartilage; smooth muscle regulates airflow.

• Conducting Zone:
    - Definition: Pathway that moves, warms, humidifies, and filters air; includes trachea, bronchi, and bronchioles to terminal bronchioles.

• Respiratory Zone:
    - Definition: Site of gas exchange; includes respiratory bronchioles, alveolar ducts, and alveoli.

• Pleura:
    - Description: Membrane surrounding the lungs that reduces friction during breathing.

• Mediastinum:
    - Definition: Central thoracic compartment that contains the heart and other structures, not covered by lung membranes.

Digestive System

• Mucosa:
    - Description: Inner layer in direct contact with gastrointestinal (GI) contents; functions in protection, secretion, and absorption.

• Submucosa:
    - Description: Connective tissue layer containing blood vessels and nerves.

• Muscularis Externa:
    - Function: Responsible for peristalsis and segmentation processes in the GI tract.

• Serosa:
    - Description: Outer covering of the digestive organs.

• Stomach:
    - Function: Involved in mechanical mixing and chemical digestion of food.

• Pyloric Sphincter:
    - Function: Controls the movement of chyme from the stomach into the duodenum.

• Duodenum:
    - Description: First part of the small intestine, receiving chyme, bile, and pancreatic secretions.

• Jejunum:
    - Description: Main area for nutrient absorption.

• Ileum:
    - Description: Final absorption area before contents empty into the cecum.

• Cecum:
    - Description: First part of the large intestine.

• Colon:
    - Function: Absorbs water and electrolytes, forms feces.

• Accessory Organs:
    - Salivary Glands: Secrete saliva.
    - Liver: Produces bile.
    - Gallbladder: Stores and concentrates bile.
    - Pancreas: Secretes digestive enzymes and bicarbonate into the small intestine.

Urinary System

• Renal Hilus:
    - Definition: Entry and exit point for renal vessels, nerves, lymphatics, and ureter.

• Cortex:
    - Description: Outer region of the kidney; contains glomeruli for filtration.

• Medulla:
    - Definition: Inner region which contains renal pyramids and loops of Henle.

• Renal Pyramids:
    - Contain nephron tubules and collecting ducts.

• Glomerulus:
    - Description: Capillary tuft involved in filtration of blood.

• Bowman's Capsule:
    - Function: Collects filtrate from the glomerulus.

• Proximal Convoluted Tubule (PCT):
    - Major site for reabsorption of water, ions, and nutrients.

• Loop of Henle:
    - Creates a concentration gradient for water and salt handling.

• Distal Convoluted Tubule (DCT):
    - Involved in further regulation of ions and pH balance.

• Collecting Duct:
    - Site for final adjustments of urine concentration before excretion.

• Ureter:
    - Carries urine from the kidney to the bladder.

• Bladder:
    - Storage vessel for urine.

• Urethra:
    - Carries urine to the exterior of the body.

Cardiovascular System

Heart Structure → Function

• Right Atrium:
    - Function: Receives deoxygenated blood from the body.

• Right Ventricle:
    - Function: Pumps deoxygenated blood to the lungs for gas exchange.

• Left Atrium:
    - Function: Receives oxygenated blood from the lungs.

• Left Ventricle:
    - Function: Pumps oxygenated blood to the rest of the body; has the strongest muscular wall.

• Valves:
    - Tricuspid Valve:
      - Pathway: Right Atrium → Right Ventricle.
    - Mitral (Bicuspid) Valve:
      - Pathway: Left Atrium → Left Ventricle.
    - Pulmonary Semilunar Valve:
      - Pathway: Right Ventricle → Pulmonary Trunk.
    - Aortic Semilunar Valve:
      - Pathway: Left Ventricle → Aorta.

• Other Structures:
    - Septum:
      - Function: Separates the left and right sides of the heart.
    - Chordae Tendineae:
      - Function: Prevents valve prolapse during ventricular contraction.
    - Papillary Muscles:
      - Function: Stabilize heart valves.

Vessels

• Arteries:
    - Function: Carry blood away from the heart; possess thick walls.
• Veins:
    - Function: Carry blood toward the heart; equipped with valves to prevent backflow.
• Capillaries:
    - Function: Site of exchange of substances; one cell thick facilitating diffusion.

Major Vessels

• Aorta: - Major artery from the heart carrying oxygenated blood.
• Pulmonary Arteries:
    - Carry deoxygenated blood to the lungs.
• Pulmonary Veins:
    - Carry oxygenated blood from the lungs to the heart.
• Superior Vena Cava:
    - Drains blood from the upper body into the right atrium.
• Inferior Vena Cava:
    - Drains blood from the lower body into the right atrium.

Structure → Function Links

• Left Ventricle Thickness:
    - Requires thicker muscular walls to pump blood throughout the body.
• Valve Functionality:
    - Prevents backflow of blood during contraction and relaxation phases of the heart.
    - Vein Valve Functionality:
      - Prevents pooling of blood in extremities.
• Capillary Structure:
    - Thin walls support diffusion processes for nutrient and gas exchange.
• Elastic Artery Structure:
    - Designed to withstand and regulate high blood pressures.

Exam Traps

• Pulmonary Arteries:
    - Deoxygenated blood, often confused with oxygenated blood pathways.
• Pulmonary Veins:
    - Carry oxygenated blood back to the heart, opposite to the arteries.
• Mitral Valve:
    - Also known as the bicuspid valve, located on the left side of the heart.
• Tricuspid Valve:
    - Positioned on the right side of the heart.
• Clarification: Blood does not flow directly from atrium to artery or from ventricle to vein directly without passing the valves.