Lymphatic System: Functions and Cells

Lymphatic System Overview

• Phagocytosis is when immune cells like macrophages and neutrophils engulf pathogens, dead cells, or debris
• Cisterna Chyli is a sac in the lymphatic system that collects lymph from the lower limbs and intestines, then drains into the thoracic duct
• Immunocompetent immune cells are mature, fully functional, and ready to recognize and respond to pathogens
• B Lymphocytes (B cells) create antibodies and play a role in antibody-mediated immunity that mark enemies for destruction
• Fixed Macrophages act as security guards in place in tissues to catch invaders
• Immunoglobulins are antibodies made by B cells to bind and neutralize foreign antigens
• Lysozymes are enzymes in tears, saliva, and mucus that destroy bacterial cell walls and act as a natural bacteria-killer in bodily fluids for defense
• Opsonization is when a pathogen is tagged with antibodies or proteins to make it easier for phagocytes to find and eat

Lymphatic System Functions

• The lymphatic system drains excess interstitial fluid that leaks into tissues after blood delivers nutrients, preventing swelling (edema)
• Lacteals, special lymphatic capillaries in the small intestine, absorb dietary fats and fat-soluble vitamins (A, D, E, K) and transport them to the bloodstream via lymph
• Lymph nodes filter lymph and expose it to immune cells like B and T lymphocytes to detect and respond to infections or abnormal cells

MALT (Mucosa-Associated Lymphatic Tissue)

• MALT is a collection of small lymphoid tissues found in mucous membranes of the digestive, respiratory, urinary, and reproductive tracts
• MALT includes
  • Tonsils in the throat
  • Peyer's patches in the small intestine
  • The appendix
  • Lymphoid tissue in airways
• MALT acts as the first line of immune defense where pathogens are likely to enter the body
• MALT contains B and T cells ready to fight off microbes, guarding the body's openings

Thymus Gland

• The thymus is in the upper chest, just above the heart
• The primary function of the thymus is to mature T lymphocytes (T cells), making them immunocompetent
• The thymus is largest and most active during childhood, and shrinks with age

Steps of Phagocytosis

• Chemotaxis: A phagocyte senses chemicals from pathogens or damaged cells and moves toward them
• Adherence: The phagocyte sticks to the target, with the help of opsonization (marking with antibodies)
• Ingestion: The phagocyte wraps its membrane around the target and pulls it inside, forming a sac called a phagosome
• Digestion: The phagosome fuses with a lysosome that digests the invader
• Exocytosis: The leftover bits are expelled from the cell

Key Lymphoid Cells

• B lymphocytes (B cells) make antibodies and memory B cells to help fight future infections faster
• T Lymphocytes (T cells):
  • Helper T cells (CD4+) activate other immune cells
  • Cytotoxic T cells (CD8+) kill infected or cancerous cells
• Natural Killer (NK) Cells are part of innate immunity and destroy abnormal cells like tumor or virus-infected cells
• Macrophages & Dendritic Cells perform phagocytosis and present antigens to activate T cells, bridging innate and adaptive immunity

Respiratory System structures

• Carina is a ridge of cartilage where the trachea splits into the left and right pulmonary bronchi which triggers a strong cough to protect the lower respiratory tract
• Elastic Recoil is the natural tendency of the lungs and chest wall to return to shape after inhalation, which helps in exhalation
• Surface tension in the fluid lining the alveoli makes them want to collapse; surfactant reduces this tension for efficient gas exchange
• Compliance refers to how easily the lungs and thoracic wall can expand, decreased by factors like scar tissue, fluid, or lack of surfactant
• Apnea is a temporary halt in breathing, occurring voluntarily or involuntarily
• Total Lung Capacity (TLC) is the total amount of air lungs can hold after max inhalation ie; TLC = vital capacity (VC) + residual volume (RV)
• Residual Volume is the air remaining in the lungs after forceful exhalation, preventing lung collapse
• Tidal Volume is the amount of air breathed in and out during normal relaxed breathing, approximately 500mL in an average adult

Respiratory System Functions

• Gas Exchange occurs in the alveoli of the lungs.
  • External respiration moves O₂ from the air into the blood, and CO₂ moves from the blood into the lungs to be exhaled
  • Internal respiration moves O₂ from the blood into body tissues, and CO₂ moves from tissues into blood
• Regulation of Blood pH balances pH levels by dissolving CO₂ in the blood to form carbonic acid (H₂CO₃)
  • Too much CO₂ leads to acidic blood (low pH)
  • Breathing faster removes CO₂, raising pH (less acidic)
• Voice Production (Phonation) use vocal folds in the larynx to vibrate when air moves through them to produce sound, with pitch controlled via tension or length of vocal cords
• Olfaction (Smell) is made possible when airborne chemicals stimulate olfactory receptors in the nasal cavity, sending signals to the brain
• Protection (Air Filtering & Defense) involves nose hairs, mucus, cilia, coughing, sneezing, and alveolar macrophages

Alveolar Cells

• Type I Alveolar Cells
  • These make up 95% of the alveolar wall
  • They are structured for gas exchange by being thin.
• Type II Alveolar Cells
  • They secrete surfactant to reduce surface tension and maintain inflation
  • Without surfactant, alveoli would collapse.
• Alveolar Macrophages eat and clear bacteria, as well as dust & polution

Respiration

• Active Inhalation increases thoracic volume, which lowers pressure inside lungs
• Passive Exhalation occurs via elastic recoil
• Active Exhalation occurs while contracting muscles to breath

Gas Laws for the Respiratory System

• Boyle’s Law describes that increased volume = decreased pressure
• Frank-Starling’s Law describes that more blood returns to the heart
• Henry’s Law Describes that carbon Dioxide dissolves easier in the blood and is regulated by breathing pattern
• The body has breathing patterns which depend on activity, emotion, and medical coditions

Breathing Patterns

• Eupnea is a normal, quiet breathing at rest
• Apnea is the temporary cessation or pause of breathing
• Dyspnea is difficult or labored breathing
• Tachypnea is rapid breathing
• Costal breathing is shallow breathing using the rib cage muscles
• Diaphragmatic breathing is deep breathing using the diaphragm

Hemoglobin's Role

• Hemoglobin is a protein in red blood cells which carries up to 4 oxygen molecules
• The curve indicates how the conditions affect saturation

Hemoglobin and the Oxygen Dissociation Curve

• The Y-axis indicates % saturation of hemoglobin
• The X-axis indicates partial pressure of oxygen, showing lungs saturation level
• The curve flattens during oxygen bond
• During oxygen deprivation the curve is steep

Shifting the Curve

• The curve shifts in relation to body activity
• Right shift means more oxygen is released.
• Low pH triggers hemoglobin to react for a release
• Low temp triggers hemoglobin to withhold oxygen

More on the Curve

• The curve balances oxygen need for activity
• Regulation of CO2, temperature etc regulates hemoglobin level too

Nerve Impact on breathing

• The brainstem controls the rate and depth of breathing & is involuntary
• The medulla oblongata has the main control center that sets the basic rhythm
• The pons modifies rhythm and smooth transitions

Apneustic/Pneumotaxic Centers

• The pons fine-tunes breathing, balancing smooth breathing

Breathing Conditions

• Hypercapnia is too much CO2 levels
• Hypocapnia is high PH level from less CO2

Kidney Basics

• Glomerulus: Ball of capillaries inside renal corpuscles for blood filtration
• Myogenic Mechanism: Maintains stable GFR despite blood pressure changes by constricting/dilating afferent arteriole
• Baroreceptor: Pressure-sensing receptor in blood vessels
• Macula Densa: Cells in nephron loop detect sodium and flow rate in filtrate
• Principal Cells: Cells in distal tubule/collecting duct that reabsorb sodium & secrete potassium
• Podocytes: Specialized cells in Bowman's capsule that wrap around capillaries
• Pedicels: Foot-like extensions of podocytes that interlock and create filtration slits to block proteins and cells

Kidney Anatomy

• Kidneys are bean-shaped located behind peritoneum and responsible for filtering blood and producing urine

Kidney internal anatomy

• The renal hilum is the entry/exit site to renal tissue
• Connective tissues are the fascia, adipose and renal capsule tissue
• Thecortex is the outer layer, containing the nephron tissue
• Renal medulla is the coned tissue with tissue to drain urine

Nephron Physilogy

• The million nephrons filte absorb & filtrate, creating urine

Key Process

• Filtration occurs in renal corpuscle
• Reabsorption happens in te tubule
• Secretion ocuurs to excrete in blood to urine

Urine System - functions

• Filtration and excretion remove waste product The kidney system balances fluid and regulates blood pH by reabsorption
• The kidney produces hormones
• Kidneys maintain osmomarity and glucose by balancing solutes and glucogensis

Section

• Cortex is the outer layer of glomeri tissue
• Medulla is they inner lary with pyramids the order is medulla -> papilla -> calyx -> pelvis -> uterere

Nephrons

• Crtical Nephrons are in the outer cortex
• Juxtamedullary Nephron concentrates urine

JGA function

• The JGA assists with ascending the nephorn for blood and GFR regulation

Water types

• In the nephron loop 90% or water as reabsorbed. DCT adjusts

Kidney and Salt

• The kidney concentrates urine, filtering, and balancin salt

Kidney Function

• The process empies the bladder & is in/voluntary
• Nerves trigger the muscles and urethra
• Blood is filtered and urine is created
• Fluids, electrolytes, and blood pressure are all controlled

Filtration

• After the glomerulus filters ions and is absorbed, the ascending allows absoroption and filters again with ducts to produce urine

RAA System

• The process begins to raise BP to trigger sodium levels

Kidney tissue

• Three outer layers are protected by connective tissue

Kidney Sequence and flow

• "R-S-I-A-C → Afferent → Glomerulus → Efferent → P/V”
• Blood flows and balances in a filtration
• Wastes are removed