Respiration occurs in three steps :
1- Mechanical ventilation : inhaling and exhaling of air between lungs and atmosphere.
2- Gas exchange : between pulmonary alveoli and pulmonary capillaries.
3- Transport of gases from the lung to the peripheral tissues , and from the peripheral tissues back to blood .
These steps are well regulated by neural and chemical regulation.

Respiratory tract is subdivided into upper and lower respiratory tract. The upper respiratory tract involves , nose , oropharynx and nasopharynx , while the lower respiratory tract involves larynx , trachea , bronchi ,and lungs .

Nose fulfills three important functions which are :

1. warming of inhaled air .

b. filtration of air .

c. humidification of air .

Pharynx is a muscular tube , which forms a passageway for air and food .During swallowing the epiglottis closes the larynx and the bolus of food falls in the esophagus .

Larynx is a respiratory organ that connects pharynx with trachea . It is composed of many cartilages and muscles and

vocal cords . Its role in respiration is limited to being a conductive passageway for air .

Trachea is a tube composed of C shaped cartilage rings from anterior side, and of muscle (trachealis muscle ) from its posterior side.The rings prevent trachea from collapsing during the inspiration. 

From  the trachea the bronchi are branched into right and left bronchus ( primary bronchi) , which enter the lung .Then they repeatedly branch into secondary and tertiary bronchi and then into terminal and respiratory broncholes.There are about 23 branching levels from the right and left bronchi to the respiratory bronchioles  , the first upper  17 branching are considered as a part of the conductive zones , while the lower 6 are considered to be respiratory zone. 

The cartilaginous component decreases gradually from the trachea to the bronchioles  . Bronchioles are totally composed of smooth muscles ( no cartilage) . With each branching the diameter of bronchi get smaller , the smallest diameter of respiratory passageways is that of respiratory bronchiole. 

Lungs are evolved by pleura . Pleura is composed of two layers : visceral and parietal .
Between the two layers of pleura , there is a pleural cavity , filled with a fluid that decrease the friction between the visceral and parietal pleura.
 

Respiratory muscles : There are two group of respiratory muscles:

1. Inspiratory muscles : diaphragm and external intercostal muscle ( contract during quiet breathing ) , and accessory inspiratory muscles : scaleni , sternocleidomastoid , internal pectoral muscle , and others( contract during forceful inspiration).
 

2. Expiratory muscles : internal intercostal muscles , and abdominal muscles ( contract during forceful expiration)

Functions

Manufacture - blood proteins - albumen, clotting proteins , urea - nitrogenous waste from amino acid metabolism , bile - excretory for the bile pigments, emulsification of fats by bile salts

Storage - glycogen , iron - as hemosiderin and ferritin , fat soluble vitamins A, D, E, K

Detoxification -alcohol , drugs and medicines , environmental toxins

Protein metabolism -

• transamination - removing the amine from one amino acid and using it to produce a different amino acid. The body can produce all but the essential amino acids; these must be included in the diet.
• deamination - removal of the amine group in order to catabolize the remaining keto acid. The amine group enters the blood as urea which is excreted through the kidneys.

Glycemic Regulation - the management of blood glucose.

• glycogenesis - the conversion of glucose into glycogen.
• glycogenolysis - the breakdown of glycogen into glucose.

gluconeogenesis - the manufacture of glucose from non carbohydrate sources, mostly protein

Bile - produced in the liver and stored in the gallbladder, released in response to CCK . Bile salts (salts of cholic acid) act to emulsify fats, i.e. to split them so that they can mix with water and be acted on by lipase.

Pancreatic juice: Lipase - splits fats into glycerol and fatty acids. Trypsin, and chymotrypsin - protease enzymes which break polypeptides into dipeptides. Carboxypeptidase - splits dipeptide into amino acids. Bicarbonate - neutralizes acid. Amylase - splits polysaccharides into shorter chains and disaccharides.

Intestinal enzymes (brush border enzymes): Aminopeptidase and carboxypeptidase - split dipeptides into amino acids. Sucrase, lactase, maltase - break disaccharides into monosaccharides. Enterokinase - activates trypsinogen to produce trypsin. Trypsin then activates the precursors of chymotrypsin and carboxypeptidase. Other carbohydrases: dextrinase and glucoamylase. These are of minor importance.

Cystic Fibrosis
→ Thick mucus coagulates in ducts, produces obstruction, Too thick for cilia to move
 
→ Major Systems Affected: Respiratory System, G. I. Tract,Reproductive Tract

→ Inherited, autosomal recessive gene, most common fatal genetic disorder

→    Major characteristic, Altered electrolyte composition (Saliva & sweat Na+, K+, Cl-)

→    Family history of Cystic Fibrosis
→    Respiratory Infections & G.I.Tract malabsorption
→    Predisposes lung to Secondary infection (Staphylococcus, Pseudomonas)
→    Damages Respiratory Bronchioles and Alveolar ducts, Produces Fibrosis of Lungs, Large cystic dilations)

The pituitary gland is pea-sized structure located at the base of the brain. In humans, it consists of two lobes:

• the Anterior Lobe and
• the Posterior Lobe

The Anterior Lobe

The anterior lobe contains six types of secretory cells All of them secrete their hormone in response to hormones reaching them from the hypothalamus of the brain.

Thyroid Stimulating Hormone (TSH)

TSH (also known as thyrotropin) is a glycoprotein The secretion of TSH is

• stimulated by the arrival of thyrotropin releasing hormone (TRH) from the hypothalamus.
• inhibited by the arrival of somatostatin from the hypothalamus.

 TSH stimulates the thyroid gland to secrete its hormone thyroxine (T₄).

Some develop antibodies against their own TSH receptors making more T₄ causing hyperthyroidism. The condition is called thyrotoxicosis or Graves' disease.

Hormone deficiencies

A deficiency of TSH causes hypothyroidism: inadequate levels of T₄ (and thus of T₃ )..

Follicle-Stimulating Hormone (FSH)

FSH is a heterodimeric glycoprotein Synthesis and release of FSH is triggered by the arrival from the hypothalamus of gonadotropin-releasing hormone (GnRH).

FSH in females :In sexually-mature females, FSH (assisted by LH) acts on the follicle to stimulate it to release estrogens.

FSH in males :In mature males, FSH acts on spermatogonia stimulating (with the aid of testosterone) the production of sperm.

Luteinizing Hormone (LH)

LH is synthesized within the same pituitary cells as FSH and under the same stimulus (GnRH). It is also a heterodimeric glycoprotein

LH in females

In sexually-mature females, LH

• stimulates the follicle to secrete estrogen in the first half of the menstrual cycle
• a surge of LH triggers the completion of meiosis I of the egg and its release (ovulation) in the middle of the cycle
• stimulates the now-empty follicle to develop into the corpus luteum, which secretes progesterone during the latter half of the menstrual cycle.

LH in males

LH acts on the interstitial cells (also known as Leydig cells) of the testes stimulating them to synthesize and secrete the male sex hormone, testosterone.

LH in males is also known as interstitial cell stimulating hormone (ICSH).

Prolactin (PRL)

Prolactin is a protein of 198 amino acids. During pregnancy it helps in the preparation of the breasts for future milk production. After birth, prolactin promotes the synthesis of milk.

Prolactin secretion is

• stimulated by TRH
• repressed by estrogens and dopamine.

Growth Hormone (GH)

• Human growth hormone (also called somatotropin) is a protein
• The GH-secreting cells are stimulated to synthesize and release GH by the intermittent arrival of growth hormone releasing hormone (GHRH) from the hypothalamus. GH promotes body growth

In Child

• hyposecretion of GH produces dwarfism
• hypersecretion leads to gigantism

In adults, a hypersecretion of GH leads to acromegaly.

ACTH — the adrenocorticotropic hormone

ACTH acts on the cells of the adrenal cortex, stimulating them to produce

• glucocorticoids, like cortisol
• mineralocorticoids, like aldosterone
• androgens (male sex hormones, like testosterone

Hypersecretion of ACTH cause of Cushing's disease.

Cardiac Output:

Minute Volume = Heart Rate X Stroke Volume

Heart rate, HR at rest = 65 to 85 bpm  

Each heartbeat at rest takes about .8 sec. of which .4 sec. is quiescent period.

Stroke volume, SV at rest = 60 to 70 ml.

Heart can increase both rate and volume with exercise. Rate increase is limited due to necessity of minimum ventricular diastolic period for filling. Upper limit is usually put at about 220 bpm. Maximum heart rate calculations are usually below 200. Target heart rates for anaerobic threshold are about 85 to 95% of maximum.

Terms:

End Diastolic Volume, EDV - the maximum volume of the ventricles achieved at the end of ventricular diastole. This is the amount of blood the heart has available to pump. If this volume increases the cardiac output increases in a healthy heart.

End Systolic Volume, ESV - the minimum volume remaining in the ventricle after its systole. If this volume increases it means less blood has been pumped and the cardiac output is less.

EDV - ESV = SV

SV / EDV = Ejection Fraction The ejection fraction is normally around 50% at rest and will increase during strenuous exercise in a healthy heart. Well trained athletes may have ejection fractions approaching 70% in the most strenuous exercise.

Isovolumetric Contraction Phase - a brief period at the beginning of ventricular systole when all valves are closed and ventricular volume remains constant. Pressure has risen enough in the ventricle to close the AV valves but not enough to open the semilunar valves and cause ejection of blood. 

Isovolumetric Relaxation Phase - a brief period at the beginning of ventricular diastole when all valves are closed and ventricular volume is constant. Pressure in the ventricle has lowered producing closure of the semilunar valves but not opening the AV valves to begin pulling blood into the ventricle.

Dicrotic Notch - the small increase in pressure of the aorta or other artery seen when recording a pulse wave. This occurs as blood is briefly pulled back toward the ventricle at the beginning of diastole thus closing the semilunar valves.

Preload - This is the pressure at the end of ventricular diastole, at the beginning of ventricular systole. It is proportional to the End Diastolic Volume (EDV), i.e. as the EDV increases so does the preload of the heart. Factors which increase the preload are: increased total blood volume, increased venous tone and venous return, increased atrial contraction, and the skeletal muscular pump.

Afterload - This is the impedence against which the left ventricle must eject blood, and it is roughly proportional to the End Systolic Volume (ESV). When the peripheral resistance increases so does the ESV and the afterload of the heart. 

The importance of these parameters are as a measure of efficiency of the heart, which increases as the difference between preload and afterload increases