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Healing and Repair - Pathology (view source)
Revision as of 16:32, 25 July 2011
, 16:32, 25 July 2011no edit summary
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{{toplink
−|linkpage =General Pathology
−|linktext =General Pathology
−|maplink = General Pathology (Content Map)
−|pagetype =Pathology
−|sublink1=Inflammation - Pathology
−|subtext1=INFLAMMATION
−}}
−<br>
''Back to [[Integumentary System - Pathology|Integumentary System Pathology]]
−* Healing of a wound or surgical incision may be by:
−** '''First intention'''
−** '''Second intention'''.
−
−===Healing by First Intention===
−
−* Healing by first intention occurs when the incised ends remain in close apposition to each other anf bacterial contamination is minimal.
−** This may be induced by suturing.
−** For example, a surgical incision.
−* Results in minimal scarring.
−
−====Process====
−
−* Initially, the incision ruptures the dermal blood vessels.
−** The exuded blood forms a fibrinous clot between and above the incision.
−*** The clot functions to:
−***# Stem the flow of blood from the injured site.
−***# Adhere the two ends together.
−***# Prevent infection from entering the injured area.
−* The basal layer of epithelium wthin 1mm of the wound edge begins to lose its connections with adjacent basal and overlying epithelium.
−** Undergoes mitosis.
−** Begins to migrate down both sides of the wound under the clot using pseudopodia.
−*** As they are migrating, cells differentiate to some degree to form more superficial layers of the epithelium.
−**** Gives a rather thick, if not very strong, barrier of epidermis.
−*** In the area of migration, the skin is usually hypopigmented and lacks hair follicles.
−* Within 2-4 days, the migrating basal layer of epithelium from either side meet together under the clot.
−** It is thought that there is passage of substances, from one side to another that prevents further migration and mitosis.
−** This gives reconstituion of an intact barrier to micro-organisms.
−* While the epithelial changes are occuring, there is a sudden proliferation of local fibroblasts and accompanying endothelial cells in the dermis surrounding the incision.
−** These grow across the narrow divide from each side and link up in the middle.
−*** Takes about 12 hours to accomplish.
−** In the early stages (days 4-7), their alignment may be vertical, but in later stages (7-21 days) both fibroblasts and capillaries line up horizontally across the incision.
−** This dermal repair forms the major portion of strength between the two sides at this time.
−*** Gains in strength over a long period of time as the collagen contracts and remodels according to the stresses imposed upon it.
−
−====Factors Inhibiting Healing====
−
−* Factors inhibiting proper wound healing include:
−*# '''Protein deficiency'''
−*#* May be absolute, as in starvation, or resolute, as in some of the endocrine deficiencies.
−*#** E.g. [[Thyroid Gland - Pathology#Hypothyroidism|hypothyroidism]]
−*# '''Vitamin C deficiency '''
−*#* Vitamin C is essential for fibroplasia and to maintain the integrity of endothelial and epithelial cells.
−*# '''Cold'''
−*# '''Ageing'''
−*# '''Contamination'''
−*#* Infection tends not to be a complication as bacteria are generally excluded.
−*#** Retained foreign material such as hair portions or suture material inadvertently left in the wound will cause infection and/or a foreign body reaction.
−*# '''Movement'''
−*#* Gives persistent trauma.
−
−===Healing by Second Intention===
−
−* Healing by second intention occurs when the gap between the ends of the incision is too wide to allow close approximation of the ends.
−* This process of granulation tissue repair in a large wound is also the underlying process in the repair of:
−** Infarcts and thrombi in vessels.
−** Surface ulcers and diphtheresis.
−** Pyogenic membrane in abscesses.
−** Diffuse fibrosis ( cirrhosis ) in the [[Liver - Anatomy & Physiology|liver]].
−
−====Process====
−
−* In comparison to healing by first intention, there is a more massive fibroblastic and endothelial proliferation in the wound which fills and repairs the defect.
−* There is also considerable surface exudation.
−** The exudate is composed of fibrinous fluid and numerous inflammatory cells, mainly [[Neutrophils|neutrophils]] and macrophages.
−*** The cells are scavengers, and engulf necrotic debris and any bacteria present
−*** Macrophages and their secretions are also important for the promotion of fibroplasia.
−* The fibroblasts tend to align themselves roughly horizontal to the surface, but the endothelium is perpendicular to the surface.
−** The upper vessels form loops near to the surface.
−*** Gives the gross appearance of red granules - this is [[Granulation Tissue|granulation tissue]].
−* Well-formed granulation tissue tends to be fairly resistant to surface infection; however, it is rather delicated and so susceptible to trauma and subsequent introduction of infection.
−** Infection is therefore a common complication in the early stages of healing.
−* Once the gap has been filled with granulation tissue and is free of infection, the epithelium migrates across.
−** As it migrates, the epithelium secretes collagenolytic substances.
−* The epidermis is usually hypopigmented and lacks hair follicles unless they have survived in the granulation tissue.
−
−==== Factors Inhibiting Healing====
−
−* Several factors inhibit healing by second intention.
−*# '''Movement'''
−*#* Movement before sufficient strength has been attained in the bond between the edges can inhibit healing.
−*# '''Infections'''
−*# '''Corticosteroids'''
−*#* Prevent proper collagen matrix formation.
−*#* Inhibit leukocyte emigration and phagocytosis.[[Image:scar tissue.jpg|thumb|right|150px|Scar tissue (Courtesy of BioMed Archive)]]
−*#* Diminish any acute inflammatory response by generally stabilising cellular membranes.
−
−====Scarring====
−
−* As the fibroblasts mature into fibrocytes, the collagen also matures and contracts and there may be extensive scar formation.
−** There may be considerable depression of the surface in such a scar.
−** The scar may interfere with movement in the area.
−* The scar tends to diminish in size over a long period of time, as the underlying collagen remodels according to the stresses imposed upon the area.
−
−==Repair in the Bones==
−
−===Causes of Fracture===
−
−* The causes of fracture fit into two distinct categories:
−*# '''Fracture of trauma'''
−*#* Breakage of normal healthy bone due to excessive stress pressure of short duration.
−*# '''Pathological fracture'''
−*#* Breakage of bone weakened by some underlying metabolic, inflammatory or neoplastic condition.
−
−===Description of a Fracture===
−
−* There are various terms to describe a fracture's appearance.
−* Separation of the ends of the fracture may be '''complete''' or '''incomplete'''.
−* When there is no penetration of the overlying skin, a the fracture is described as '''closed'''.
−* When the sharp ends penetrate the overlying skin, the fracture is '''compound'''.
−** In this scenario there is the danger of introducing infection.
−*'''Comminuted''' describes a fracture where there are multiple small fragments of bone at the site of breakage.
−* Where the edges of the fracture are impacted into each other, the fracture is said to be '''compressed'''.
−* When one side of the fracture is depressed below the plane of the other, the term '''depressed''' is used.
−** This occurs in the flat bones of the skull.
−* '''Microfractures''' are fractures that are only visible on histological section as cracks in the bone.
−** Grossly, there might be evidence of some haemorrhage in the area.
−
−===Fracture Repair===
−[[Image:fracture repair.jpg|thumb|right|150px|Fracture repair (Courtesy of BioMed Archive)]]
−* On breakage, there is rupture of the periosteal, cortical and medullary vessels, causing:
−** A blood clot in the breakage area.
−*** Fibrin is the important component.
−** Local necrosis of tissue supplied by these vessels.
−*** This lowers the local pH.
−* The fate of the blood clot depends upon its location.
−** The periosteal portion is lysed and disappears;
−** The medullary portion is removed by macrophages.
−* The necrotic material is removed by phagocytosis.
−** Necrotic [[Bone Marrow - Anatomy & Physiology|bone marrow]] is removed by [[Macrophages|macrophages]].
−*** This is a fairly rapid process.
−** Osteoclasts remove necrotic bone.
−*** This is a slow process.
−* On the periosteal side, the periosteum proliferates into the clot.
−** Forms a fibrous collar around the bone called the soft callus.
−* The cells in the inner aspect of the soft callus, particularly those near the fracture fragments, differentiate into osteoblasts. [[Image:fracture callus.jpg|thumb|right|150px|Fracture callus (Courtesy of BioMed Archive)]]
−** Grow across the divide between the two fragments, laying down coarse woven bone.
−* The woven bone laid is known as the hard callus.
−** This periosteal coarse bone is of utmost importance in repair.
−*** It is responsible for much of the strength of the fracture repair.
−** This is replaced over a period of time by mature compact bone.
−*** Aligns itself according to the stresses applied to it.
−* Periosteal cells that are further away from the fracture fragments differentiate into cartilage-producing cells.
−** Produce a cone of cartilage between the two fragments.
−*** As the local pH changes to more alkaline conditions, this cartilage undergoes calcification, with invasion by blood vessels and osteoblasts.
−**** The cartilage is replaced by bone - endochondral ossification.
−* On the medullary side, the endosteum proliferates and invades the clot, laying down bone.
−** This bone may totally occlude the medulla and is later remodelled to reconstitute a patent lumen.
−
−===Complications===
−
−* There are several possible complications that may arise in the repair of bone.
−# Inadequate immobilisation of the fractured ends will lead to incomplete repair by callus formation.
−#* An intervening mass of fibrocartilage remains, forming a false joint.
−#** In some cases the false joint can even appear to form a synovial lining.
−#* If the fractured ends are sufficiently far apart, no substantial callus forms.
−#** The intervening space is taken up by connective tissue organisation.
−# Failure to align the fractured ends in proper apposition to one another will produce excessive callus.
−#* This takes a longer time to be remodelled by the adult compact bone.
−# [[Healing and Repair - Pathology#Description of a Fracture|Comminution]] delays healing due to persistent irritation.
−# Infection delays healing due to the effects of the toxins on theproliferating cells.
−#* May give rise to a systemic infection affecting the rest of the body.
−
+
{{review}}
{{review}}
−==Introduction==
==Introduction==
−* There are several factors on which the ability to heal and repair depends:
* There are several factors on which the ability to heal and repair depends:
*# '''Species'''
*# '''Species'''
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==Repair==
==Repair==
−* Repair occurs through one of two mechanisms:
* Repair occurs through one of two mechanisms:
** '''Regeneration'''
** '''Regeneration'''
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===Regeneration===
===Regeneration===
−* In mammals, only epithelial and connective tissues regenerate extensively.
* In mammals, only epithelial and connective tissues regenerate extensively.
* The ability of tissue to regenerate depends upon whether the tissue is
* The ability of tissue to regenerate depends upon whether the tissue is
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====Labile Tissues====
====Labile Tissues====
−* Labile tissues constantly replenish their cells throughout life.
* Labile tissues constantly replenish their cells throughout life.
** For example skin and mucous epithelia normally desquamate their outer layer of cells during life, maintaining their overall composition by division of their basal layers.
** For example skin and mucous epithelia normally desquamate their outer layer of cells during life, maintaining their overall composition by division of their basal layers.
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====Stable Tissues====
====Stable Tissues====
−* Stable tissues have a limited ability to replace themselves.
* Stable tissues have a limited ability to replace themselves.
* They retain the ability to
* They retain the ability to
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====Permanent====
====Permanent====
−* Permanent tissues have poor or no regenerative capacity.
* Permanent tissues have poor or no regenerative capacity.
* This group includes tissues in which the cells are highly specialised and generally have only one function, for example:
* This group includes tissues in which the cells are highly specialised and generally have only one function, for example:
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===Replacement===
===Replacement===
−* Replacement is essentially endothelial and fibrous tissue proliferation to replace severely damaged tissue.
* Replacement is essentially endothelial and fibrous tissue proliferation to replace severely damaged tissue.
** This classical dual replacement gives rise to granulation tissue.
** This classical dual replacement gives rise to granulation tissue.
−==Repair in the Skin==
+==[[Skin Repair|Repair in the Skin]]==
−==[[Fractures|Repair in the Bones]]==
==Repair in the Respiratory Tract==
==Repair in the Respiratory Tract==
−* Severe damage to the alveolar wall results in fibrous tissue organisation of the entire alveolus.
* Severe damage to the alveolar wall results in fibrous tissue organisation of the entire alveolus.
* The appearance of inflammation in the respiratory tract varies with the route of entry of the agent.
* The appearance of inflammation in the respiratory tract varies with the route of entry of the agent.
===Airborne Agents===
===Airborne Agents===
−* Infectious droplets tend to deposit in the anterior ventral portions of the lobes.
* Infectious droplets tend to deposit in the anterior ventral portions of the lobes.
** I.e. in the apical, cardiac and anterior portions of the diaphragmatic lobes.
** I.e. in the apical, cardiac and anterior portions of the diaphragmatic lobes.
−* Airborne agents produce '''bronchopneumonia'''.
+* Airborne agents produce [[Bronchopneumonia|'''bronchopneumonia''']].
** So-called because the inflammation is initiated and centred upon the airways.
** So-called because the inflammation is initiated and centred upon the airways.
* The usual appearance of bronchopneumonia in ruminants and the pig is as the name suggests.
* The usual appearance of bronchopneumonia in ruminants and the pig is as the name suggests.
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*** Air trapped distal to the blockage is gradually absorbed into the bloodstream.
*** Air trapped distal to the blockage is gradually absorbed into the bloodstream.
**** This causes increased pressure on the injured wall, dilating it further.
**** This causes increased pressure on the injured wall, dilating it further.
−*** This is a progressive process and results in irreversible dilatation of the airway lumen and is called '''bronchiectasis'''.
+*** This is a progressive process and results in irreversible dilatation of the airway lumen and is called [[Bronchiectasis|'''bronchiectasis''']].
* Bronchopneumonia in the dog and cat often tends to be more diffusely spread.
* Bronchopneumonia in the dog and cat often tends to be more diffusely spread.
** These species have a poorly-developed interlobular septum and collateral ventilation between alveoli from different respiratory units.
** These species have a poorly-developed interlobular septum and collateral ventilation between alveoli from different respiratory units.
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===Blood-borne Agents===
===Blood-borne Agents===
−* Blood-bourne agents tend to have a patchy distribution throughout the lung.
* Blood-bourne agents tend to have a patchy distribution throughout the lung.
−* Cause '''interstitial pneumonia'''.
+* Cause [[Interstitial Pneumonia|'''interstitial pneumonia''']].
====Circulating Toxins====
====Circulating Toxins====
−* For example, [[Acute Bovine Pulmonary Emphysema and Oedema|"Fog Fever"]] in adult cattle.
−* For example, "Fog Fever" in adult cattle.
** Interstitial emphysema.
** Interstitial emphysema.
** 3-methyl indole is selectively toxic to Type 1 alveolar epithelium.
** 3-methyl indole is selectively toxic to Type 1 alveolar epithelium.
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====Micro-organisms====
====Micro-organisms====
−* A predominantly mononuclear reaction in the alveolar wall can be caused by:
* A predominantly mononuclear reaction in the alveolar wall can be caused by:
** Viruses
** Viruses
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*** E.g. [[Salmonella|''Salmonella'']]
*** E.g. [[Salmonella|''Salmonella'']]
** Protozoa
** Protozoa
−*** E.g. [[Toxoplasma]]
+*** E.g. ''[[Toxoplasma gondii]]''
====Parasites====
====Parasites====
−* Lungworms (''Dictyocaulus vivipara'') tend to affect the dorsocaudal areas of the diaphragmatic lobes in their invasion stage as larvae in the blood.
* Lungworms (''Dictyocaulus vivipara'') tend to affect the dorsocaudal areas of the diaphragmatic lobes in their invasion stage as larvae in the blood.
* Later adult stages irritate the airways and also release larvae which are inhaled deeper into the lung.
* Later adult stages irritate the airways and also release larvae which are inhaled deeper into the lung.
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===Traumatic Implantation===
===Traumatic Implantation===
−* Traumatic implantation is fairly rare.
* Traumatic implantation is fairly rare.
* Initially causes a pleural inflammation, with some extension to the adjacent lung tissue.
* Initially causes a pleural inflammation, with some extension to the adjacent lung tissue.
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** Stake wounds in horses.
** Stake wounds in horses.
*** Usually fatal and cause extensive purulent, smelly inflammation.
*** Usually fatal and cause extensive purulent, smelly inflammation.
−** Purulent pleuritis in dogs and cats due to [[:Category:Nocardia|''Nocardia'']] from a distant wound.
+** Purulent pleuritis in dogs and cats due to ''[[:Category:Nocardia species]]'' from a distant wound.
*** Not uncommon in cats.
*** Not uncommon in cats.
*** May take some time to develop fully after the initial wound or cause has healed.
*** May take some time to develop fully after the initial wound or cause has healed.
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==Repair in the Alimentary Tract==
==Repair in the Alimentary Tract==
−===The Gut===
===The Gut===
−* The gut is quite prone to infections.
* The gut is quite prone to infections.
** These are generally kept at bay by the profuse gut associated lymphoid tissue and the continuous movement of ingesta.
** These are generally kept at bay by the profuse gut associated lymphoid tissue and the continuous movement of ingesta.
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===The Liver===
===The Liver===
−* The [[Liver - Anatomy & Physiology|liver]] retains limited powers to regenerate and has considerable functional reserve.
* The [[Liver - Anatomy & Physiology|liver]] retains limited powers to regenerate and has considerable functional reserve.
* Acute inflammation is often due to viruses and bacteria.
* Acute inflammation is often due to viruses and bacteria.
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===The [[Pancreas - Anatomy & Physiology|Pancreas]]===
===The [[Pancreas - Anatomy & Physiology|Pancreas]]===
−* The [[Pancreas - Anatomy & Physiology|pancreas]] suffers both acute and chronic disease.
* The [[Pancreas - Anatomy & Physiology|pancreas]] suffers both acute and chronic disease.
* The acute form called acute pancreatic necrosis is the important type in dogs.
* The acute form called acute pancreatic necrosis is the important type in dogs.
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==Repair in the Urinary Tract==
==Repair in the Urinary Tract==
−* The kidney has a great functional reserve.
* The kidney has a great functional reserve.
** Only 30% of the tissue is required to function properly.
** Only 30% of the tissue is required to function properly.
===Glomerulonephritis===
===Glomerulonephritis===
−* Glomerulonephritis and glomerular deposition of amyloid may cause loss of substantial quantities of protein into the urine.
* Glomerulonephritis and glomerular deposition of amyloid may cause loss of substantial quantities of protein into the urine.
* Oedema develops in the body, generally first in the back legs, then the ventral subcutis, and perhaps in the abdominal cavity.
* Oedema develops in the body, generally first in the back legs, then the ventral subcutis, and perhaps in the abdominal cavity.
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===Pyelonephritis===
===Pyelonephritis===
−* Important in the cow and sow.
* Important in the cow and sow.
** It tends to be quite acute in the sow, and chronic in the cow.
** It tends to be quite acute in the sow, and chronic in the cow.
* Arises from infection ascending the urinary tract.
* Arises from infection ascending the urinary tract.
* There is progressive loss of tissue.
* There is progressive loss of tissue.
−** Starts with necrosis in the pelvic area, then the inflammation spreads up into the cortex. *P oor prognosis even with therapy.
+** Starts with necrosis in the pelvic area, then the inflammation spreads up into the cortex.
+*Poor prognosis even with therapy.
===Cystitis===
===Cystitis===
−* Bladder inflammation.
* Bladder inflammation.
* Common in females.
* Common in females.
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==Repair in the Genital Tract==
==Repair in the Genital Tract==
−===Female===
===Female===
−* '''Inflammation of the uterus''' in livestock can take place at two periods:
* '''Inflammation of the uterus''' in livestock can take place at two periods:
*# At service.
*# At service.
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**# Chronic mastitis.
**# Chronic mastitis.
**#* Results in progressive destruction of the glandular tissue and replacement by fibrous tissue.
**#* Results in progressive destruction of the glandular tissue and replacement by fibrous tissue.
−**#* E.g. [[Streptococcal mastitis - bovine|''Streptococcus agalactiae'']].
+**#* E.g. [[Streptococcal Mastitis - Cattle|''Streptococcus agalactiae'']].
** Some organisms such as [[Staphylococcus aureus|''Staphylococcus aureus'']] can cause gangrenous, acute and chronic mastitis.
** Some organisms such as [[Staphylococcus aureus|''Staphylococcus aureus'']] can cause gangrenous, acute and chronic mastitis.
===Male===
===Male===
−* '''Prostatitis'''
* '''Prostatitis'''
** Inflammation of the prostate.
** Inflammation of the prostate.
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==Repair in the Central Nervous System==
==Repair in the Central Nervous System==
−* '''Encephalitis'''
* '''Encephalitis'''
** Inflammation of neural tissue of the brain.
** Inflammation of neural tissue of the brain.
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** Inflammation of the meninges.
** Inflammation of the meninges.
** Purulent meningitis follows haematogenous spread of infection from umbilical infections and certain septicaemias.
** Purulent meningitis follows haematogenous spread of infection from umbilical infections and certain septicaemias.
−[[Category:Inflammation]]
+[[Category:Inflammation|B]]
+[[Category:General Pathology]]