Respiratory system is the system that helps you breath in and out, so oxygen (02) can be pumped through your body and carbon dioxide (CO2) can be removed from the blood stream, remember that the Respiratory system is made up of many different organs.
Respiratory System in Mammals
The mammalian heart is more compartmentalized than reptile lungs.
Bronchi, bronchioles, alveoli.
In each lung of a human, there are about 150.000.000 alveoli.
The alveoli for gas exchangePharinx, Trachea, larynx
Endothelial cell layer in respiratory passageway.
Mucus covering the respiratory cell surface.
Ciliated cells
Nose, nasal cavity and its function for humidification of airUpper tract
Nose, pharynx and associated structures
Lower tract
Larynx, trachea, bronchi, lungs
Alveolar Lining Regeneration
Daily turnover of about 1G/o of the type II cells, whose mitotic progeny form both type I and type 11 cells, allows for normal alveolar lining renewal. When these lining cells are destroyed by inhalation of toxic gases, replacements for both types of cells are similarly derived from the surviving type II cells. Respiratory system
Pulmonary Surfactant
Respiratory system :
It is continuously synthesized and secreted by type II alveolar cells onto the alveolar surfaces, pulmonary surfactant is removed from these surfaces by alveolar macrophages and by type I and II alveolar cells. Its composition and continuous turnover allow it to serve 2 major functions. Not only does it reduce surface tension in the alveoli, but also it is thought to have some bactericidal effects, cleaning the alveolar surface and preventing bacterial invasion of the many capillaries in the septa.
The surfactant forms a thin 2-layer film over the entire alveolar surface. The film consists of an aqueous basal layer (bypopbase) composed mainly of protein, which is covered by a monomolecular film of phospholipid (mainly di palmitoyl lecithin) whose fatty acid tails extend into the lumen. By reducing surface tension, the surfactant helps prevent collapse of the alveoli during expiration. It thus eases breathing by decreasing the force required to reopen the alveoli during the next inspiration.
Because surfac tant secretion begins in the last weeks of fetal development, premature infants often suffer a condition called hyaline membrane disease, evidenced by respiratory distress (labored Ibreathing) caused by the lack of surfactant. Surfactant secretion can be induced by administering glucocorticoids, significantly improving the infant's condition and chances for survival.
Pulmonary Surfactant:
Continuously synthesized and secreted by type II alveolar cells onto the alveolar surfaces, pulmonary surfactant is removed from these surfaces by alveolar macrophages and by type I and II alveolar cells. Its composition and continuous turnover allow it to serve 2 major functions. Not only does it reduce surface tension in the alveoli, but also it is thought to have some bactericidal effects, cleaning the alveolar surface and preventing bacterial invasion of the many capillaries in the septa. in Respiratory system the surfactant forms a thin 2-layer film over the entire alveolar surface. The film consists of an aqueous basal layer (bypopbase) composed mainly of protein, which is covered by a monomolecular film of phospholipid (mainly di palmitoyl lecithin) whose fatty acid tails extend into the lumen. By reducing surface tension, the surfactant helps prevent collapse of the alveoli during expiration. It thus eases breathing by decreasing the force required to reopen the alveoli during the next inspiration. Because surfac tant secretion begins in the last weeks of fetal development, premature infants often suffer a condition called hyaline membrane disease, evidenced by respiratory distress (labored Ibreathing) caused by the lack of surfactant. Surfactant secretion can be induced by administering glucocorticoids, significantly improving the infant's condition and chances for survival.
RESPONSE OF NERVE TISSUE TO INJURY
ØA. Damage to the Cell Body: Because mature neurons cannot divide, dead neurons cannot be replaced. Neurons not connected with otherfunctioning neurons or end organs are useless, and mechanisms have evolved to dispose of them. Thus, if a neuron makes synaptic contact with Only one other neuron and the latter is destroyed, the former undergoes autolysis, a process termed transneuronal degeneration. Most neurons, however, have multiple connections.
ØB. Damage to the Axon: Regeneration can occur in axons injured or severed Far enough from the soma to spare the cell. Such injuries are followed by partial degeneration and then regeneration. Nerve system
1. Degeneration. A crushed or severed axon degenerates both distal and proximal to the injury. Distal to the site Of injury, both the axon and myelin sheath undergo complete degeneration connection with the soma has been lost. During this Wallerian, descendent, or secondary degeneration, whichusually lakes about 2-3 days, nearby Schwann cells proliferate, phagocytose degenerated tissue, and invade the remaining endoneurial channel. Proximal to the site of injury, degeneration of the axon and myelin sheath is similar but incomplete. This retrograde, ascendent, orprimary degeneration proceeds for about 2 internodes before the injured axon is sealed. The cell body also changes in response to injury. The perikaryon enlarges; chromatolysis, or dispersion of Nissl substance, occurs; and the nucleus moves to an eccentric position. Proximal degeneration and cell body changes fake about 2 weeks.
2. Regeneration. This begins in the third week after the injury. As the perikaryon gears up for increased protein synthesis, the Nissl bodies 'eappear. The axon's proximal stump gives off a profusion of smaller processes called neurites; one of these encounters and grows into the endoneurial channel, while the others degenerate. In the channel, the neurite grows 3-4 mm/d, guided and then myelinated by the Schwann cells. Growth is maintained by orthograde axoplasmic transport of material synthesized in the soma. When the tip of the neurite reaches its termination, it connects with its end organ or another neuron in the chain. If the cut ends of a severed nerve are matched by by fascicle size and arrangement and sutured together by their epineurial sheaths within 34 weeks after injury, sensory and motor innervation can often be restored. If the gap between the cut ends is too wide, the neurites may fail to find endoneurial sheaths to grow into and may grow out in a potentially painful disorganized swelling called a neuroma. Target organs deprived of innervation often atrophy.
Alveolar Cell Types:
1. Type I cells. Also called type I alveolar cells, type I pneumocytes, and squamous alveolar cells, these are squamous epithelial cells that make up 97% of the alveolar surfaces.
They are specialized to serve as very thin (often only 25 nm in width) gas-permeable components of the blood-air barrier. Their organelles leg, Golgi complex, endoplasmic reticulum, mitochondria) cluster around the nucleus.
Much of the cytoplasm is thus unobstructed by organelles, except for the abundant small pinocytotic vesicles that are involved in the turn over of pulmonary surfactant and the removal of small particles from the alveolar surfaces. They attach to neighboring epithelial cells by desmosomes and occluding junctions.
The latter reduce pleural effusion--leakage of tissue fluid into the alveolar lumen. Type I cells can be distinguished from the nearby capillary endothelial cells by their position bordering the alveolar lumen and by their slightly more rounded nuclei.
2. Type II cells. These cells, which are also called type II alveolar cells, type II pneumocytes, great alveolar cells, and alveolar septal cells, cover the remaining 3% of the alveolar surface. They are interspersed among the type I cells, to which they attach by desmosomes and occluding junctions.
Type II cells are roughly cuboidal with round nuclei; they occur most often in small groups at the angles where alveolar septal walls converge. At the electron microscope level, they contain many mitochondria and a well-developed Golgi complex, but they are mainly characterized by the presence of large (0.2-um), membrane-limited lamellar (mutlilamellar) bodies. These structures, which exhibit many closely apposed concentric or parallel membranes (lamellae), contain phospholipids, glycosaminoglycans, and proteins.
Type II cells are secretory cells. Their secretory product, pulmonary surfactant, is assembled and stored in the lamellar bodies, which also carry it to the apical cytoplasm. There, the bodies fuse with the apical plasma membrane and release surfactant onto the alveolar surface. 3. Alveolar marcrophages. Known also as dust cells, these large monocytc-derived repre sentatives of the mononuclear phagocyte system are found both on the surface of alveolar septa and in the interstitium. Macrophages are important in removing any debris that escapes the mucus and cilia in the conducting portion of the system.
They also phagocytose blood cells that enter the alveoli as a result of heart failure. These alveolar macrophagcs, which stain positively for iron pigment (hemosiderin), are thus designated heart failure cells.
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