SEMBULINGAM PHYSIOLOGY BOOK

1. RESPIRATORY SYSTEM
DR B . S . ABARNA REDDY

2. INTRODUCTION
• RESPIRATORY SYSTEM IS INTAKE OF OXYGEN FROM ATMOSPHERE AND GIVING OUT
CARBONDI OXIDE.
• FIRST BREATH TAKES AFTER BIRTH. FETAL LUNGS ARE NON FUNCTIONAL.
• RESPIRATORY RATE
• NEWBORN 30 TO 60 BREATHS PER MIN
• ADULT 12 TO 16 BREATHS PER MIN
• TYPES OF RESPIRATION
• EXTERNAL RESPIRATION : EXCHANGE OF RESPIRATORY GASES BETWEEN LUNGS AND
BLOOD
• INTERNAL RESPIRATION : EXCHANGE OF RESPIRATORY GASES BETWEEN BLOOD AND
TISSUES.
• PHASES OF RESPIRATION
• INSPIRATORY PHASE : ACTIVE PROCESS AIR ENTER LUNGS.
• EXPIRATORY PHASE :PASSIVE PROCESS AIR LEAVES LUNGS.

3. FUNCTIONAL ANATOMY
• RESPIRATORY TRACT INCLUDES NOSE, PHARYNX ,LARYNX, TRACHEA ,BRONCHI
AND LUNGS.
• PLEURA : OUTER SEROUS MEMBRANE COVERING LUNGS.IT CONSISTS OF TWO
LAYERS
• VISCERAL LAYER: OVER SURFACE OF LUNGS.
• PARIETAL LAYER :WALL OF THORACIC CAVITY.
• PLEURAL CAVITY OR INTRAPLEURAL SPACE : BETWEEN VISCERAL AND PARIETAL
LAYER OF SEROUS MEMBRANE CONTAINS INTRAPLEURAL FLUID BY VISCERAL
LAYER
• FUNCTION : LUBRICATES , CREATES INTRAPLEURAL PRESSURE.
• ABNORMALITIES : PNEUMOTHORAX (AIR ),HYDROTHORAX (WATER) ,PYOTHORAX(

4. TRACHEOBRONCHIAL TREE
• PART OF AIR PASSAGE
• COMPONENTS : TRACHEA BIFURCATES IN TO PRIMARY BRONCHI CALLED LEFT
AND RIGHT BRONCHI.
• PRIMARY BRONCHI: DIVIDES IN TO SECONDARY BRONCHI. ENTERS THE LUNGS.
• SECONDARY BRONCHI: DIVIDES IN TO TERTIARY BRONCHIOLES .LEFT LUNG HAS
8 TERTIARY BRONCHI AND RIGHT LUNG HAS 10 TERTIARY BRONCHI.
• TERTIARY BRONCHI: REDUCE IN DIAMETER FORMING BRONCHIOLES AND
BRONCHIOLES REDUCE DIAMETER NEARLY 1MM FORMING TERMINAL
BRONCHIOLES.
• TERMINAL BRONCHIOLES : REDUCED TO 0.5 MM CALLED RESPIRATORY
BRONCHIOLES.

5. RESPIRATORY UNIT
• PARENCHYMA OF LUNGS ARE FORMED BY RESPIRATORY UNIT WHICH FORMS
TERMINAL PORTION OF RESPIRATORY TRACT.
• STRUCTURAL AND FUNCTIONAL UNIT.
• STRUCTURE
• STARTS FROM RESPIRATORY BRONCHIOLES THEN DIVIDING INTO ALVEOLAR
DUCTS .
• ALVEOLAR DUCTS ENTERS IN TO ENLARGED SAC KNOWN AS ALVEOLAR SAC
• SPACE IN ALVEOLAR SAC IS ANTRUM.
• ALVEOLAR SAC CONSISTS OF CLUSTERS OF ALVEOLI.
• ALVEOLUS IS 0.2 TO 0.5 MM AND LINED BY EPITHELIAL CELLS

6. ALVEOLAR CELLS OR PNEUMOCYTES
• ALVEOLAR EPITHELIUM HAS ALVEOLAR CELLS OR PNEUMOCYTES
• TWO TYPES OF ALVEOLAR CELLS.
• TYPE 1 ALVEOLAR CELLS : EXCHANGE OF GASES BETWEEN ALVEOLI AND BLOOD(95%)
HAS SQUAMOUS EPITHELIAL CELLS.
• TYPE 2 ALVEOLAR CELLS: GRANULAR PNUEMOCYTES .SECRETE SURFACTANT AND
ALVEOLAR FLUID.(5%) CUBOIDAL IN NATURE.
• RESPIRATORY MEMBRANE
• FORMED BY ALVEOLAR MEMBRANE OR CAPILLARY MEMBRANE
• HAS SURFACE AREA OF 70 SQ METERS AND THICKNESS OF 0.5 MICRON
• EXCHANGE OF GASES OCCURS.
• SEPARATES AIR IN ALVEOLI FROM BLOOD IN CAPILLARY.

7. NON RESPIRATORY FUNCTIONS
• OLFACTION : OLFACTORY RECEPTORS PRESET IN MUCOUS MEMBRANE OF
NOSTRILS RESPONSIBLE FOR OLFACTORY SENSATION.
• VOCALIZATION: LARYNX FORMS SPEECH APPARATUS. PLAYS MAJOR ROLE ALONE
IN VOCALIZATION PROCESS.(SOUND BOX).
• PREVENT DUST PARTICLES: DUST PARTICLES ENTERS NOSTRILS GET FILTERED BY
HAIRS IN MUCOUS MEMBRANE IF ESCAPED GETS HELD BY MUCUS BY NASAL
MUCOUS MEMBRANE.
• EVEN IT ESCAPED IT GETS FILTERED IN THE ALVEOLI BY THE PHAGOCYTIC
ACTION OF MACROPHAGES.
• DEFENSE MECHANISM : ( IMMUNOLOGICAL DEFENSE)
• CELLS IN MUCOUS MEMBRANE LINING ALVEOLI OF LUNGS ARE LEUCOCYTES
,MACROPHAGES , NK CELLS,MAST CELLS AND DENDTRIC CELLS.

8. • LUNGS OWN DEFENSE : EPITHELIAL CELLS LINING LUNGS SUCH AS
ANTIMICROBIAL PEPTIDES POLYPEPTIDES DEFENSINS AND CATHELICIDINS.
• LEUKOCYTES DEFENSE: NEUTROPHILS AND LYMPHOCYTES
• NEUTROPHILS: KILLS BACTERIA BY PHAGOCYTOSIS
• LYMPHOCYTES : PROVIDES IMMUNITY AGAINST BACTERIA.
• MACROPHAGES: SCAVENGERS IN LUNGS ENGULF DUST PARTICLES
• FUNCTION AS ANTIGEN PRESENTING CELLS IN THE DEVELOPMENT OF IMMUNITY.
• MACROPHAGES SECRETE INTERLEUKIN, TUMOR NECROSIS FACTORS AND
CHEMOKINES [ATTRACT WHITE BLOOD CELLS AT SITE OF INFLAMMATION]
• MAST CELL : PRODUCES HYPERSENSITIVITY REACTIONS. LIKE ALLERGY AND
ANAPHYLAXIS.
• SECRETS HISTAMINE, SEROTONIN ,HEPARIN AND HYDROLYTIC ENZYMES.
• DENDRITIC CELLS : FUNCTION AS ANTIGEN PRESENTING CELLS. DEVELOP
IMMUNITY.

9. • WATER BALANCE : WATER LOSS MECHANISM DURING EXPIRATION WATER
EVAPORATES
• BODY TEMPERATURE: HEAT LOSS MECHANISM DURING EXPIRATION HEAT IS
ALSO LOST.
• ACID BASE BALANCE : REGULATE CO2 IN BLOOD.CO2 ENTERS BLOOD COMBINES
WITH WATER TO FORM CARBONIC ACID .UNSTABLE SPLIT IN TO HYDROGEN AND
BICARBONATE IONS.
• CO2 IS VOLATILE GAS. MORE CO2 PRODUCED LEADS TO INCREASE HYDROGEN
ION AND REDUCE PH CAUSES HYPERVENTILATION.
• ANTICOAGULANT FUNCTION: MAST CELLS SECRETE HEPARIN .PREVENT
INTRAVASCULAR CLOTTING
• ANGIOTENSIN: ENDOTHELIAL CELLS OF PULMONARY CAPILLARIES SECRETE
ANGIOTENSIN 1 AND 2 REGULATION ECF VOLUME AND BP.
• HORMONAL SUBSTANCE SYNTHESIS: SYNTHESIZE HORMONES SUCH AS
PROSTAGLANDINS ,ACETYLCHOLINE AND SEROTONIN . INCLUDES REGULATION
OF BP.

10. RESPIRATORY PROTECTIVE REFLEXES
• COUGH REFLEX : CAUSED BY IRRITATION OF RESPIRATORY TRACT
• CAUSES BY IRRITANT AGENTS ,ALSO PRODUCED BY CARDIAC, PULMONARY DISORDERS COPD ETC., EXERT PRESSURE
ON TRACHEA ,BRONCHI AND LUNGS.
• MECHANISM: DEEP INSPIRATION WITH FORCED EXPIRATION AND CLOSED EPIGLOTTIS INCREASES INTRAPLEURAL
PRESSURE UPTO 100MMHG . VELOCITY OF AIRFLOW AT 960 KM/HR
• PATHWAY: AFFERENT NERVES :GLOSSOPHARYNGEAL, PHRENIC ,TRIGEMINAL AND VAGUS NERVE( GANI PRADI IS
WATCHING TV)
• EFFERENT NERVES : ARISE FROM MEDULLARY CENTER VIA VAGUS ,PHRENIC AND SPINAL MOTOR NERVES TO
ACTIVATE ACCESSORY MUSCLES.(PVS)
• SNEEZING REFLEX : CAUSED BY IRRITATION OF NASAL MUCOUS MEMBRANE.
• CAUSES :DUST PARTICLES, ACCUMULATION OF FLUID IN NASAL MEMBRANE
• MECHANISM : DEEP INSPIRATION WITH FORCED EXPIRATION AND OPEN EPIGLOTTIS.
• PATHWAY AFFERENT NERVES ; TRIGEMINAL AND OLFACTORY NERVE . LOCATED AT DIFFUSE SPINAL NUCLEUS OF
TRIGEMINAL NERVE, NUCLEUS SOLITARIUS AND RETICULAR FORMATION.
• EFFERENT NERVE : FROM MEDULLARY CENTER TO PHRENIC ,INTERCOSTAL, GLOSSSOPHARYNGEAL , TRIGEMINAL AND
VAGUS NERVES (PIG TV)
• SWALLOWING REFLEX : PREVENTS ENTER OF FOOD INTO AIR PASSAGE.
• DEGLUTITION APNEA OCCURS DURING 2ND PHARYNGEAL STAGE OF DEGLUTITION.