Week 5 Flashcards
(47 cards)
define a tissue
A tissue is a functional group of cell and intracellular substances
what is the name given to one or more tissues arranged into a structure that carries out a major body function?
ORGAN
The cells that carry out the main function of an organ, and are usually most abundant and often unique to the
organ are called?
parenchymal cells
What group of cells work with each other as coherent units to carry out specialized
functions, such as protection of body surfaces, secretion of hormones or enzymes, and metabolic functions
such as lipid metabolism or clearance of waste products.
EPITHELIAL CELLS
What group of cells are more loosely arranged and are involved in general support functions, such as providing physical support and facilitating the movement of fluids and nutrients
Connective tissue cells
How do our Cell Respond to Injury?
- Adaptation
When demands on the cell are
greater than before, cells adapt by increasing in number (hyperplasia)
or in size (hypertrophy); conversely, when demands on the cell are less than before, cells adapt by decreasing in number or in
size (which can cause ATROPHY). - Cells can also respond to changes in their environment by undergoing metaplasia, whereby one adult cell type is replaced by another. This usually occurs in epithelial
tissues (Squamous metaplasia). - Changes occur from Reversible and Irreversible Injury
The diminution of tissue
volume and decreased ability of the tissue to function is called?
Atrophy
it can result from a decrease in the size of cells or a decrease in their number, or both.
Labile cells (continuously divide) undergo hyperplasia
Stable cells (multiply only when needed) undergo hypertrophy
true or false?
true
When an increase in the
size of a tissue occurs because of an abnormal condition, it is called?
pathologic hypertrophy
As with hyperplasia and hypertrophy, atrophy can also be physiologic or
pathologic.
true or false
true
Types of atrophy?
- Senile atrophy: caused by aging. Tissues often become smaller and decrease in functional capacity.
- Disuse atrophy: occurs when the cells are unable to carry out their normal function. (eg: immobilized limb) Disuse atrophy may be reversible.
- Denervation atrophy: occurs when muscle cells are immobilized because of
permanent loss of nervous stimulation. - Pressure atrophy: results from steady pressure on tissue (eg: expanding tumour, Bedsores, chronically bedridden patients because of continued external pressure on the skin)
- Endocrine atrophy: results from decreased hormonal
stimulation.
when does a cell injury occur?
- cell injury occurs when an injurious stimulus is severe or the cell has exceeded
its ability to adapt. - There is Reversible and Irreversible Injury
- In reversible injury, the cell has the
potential to return to normal structure and function if the injurious stimulus is withdrawn. - Irreversible cell injury, however, leads to cell death by necrosis or apoptosis.
What is the sequence of reversible to irreversible changes
reversible changes
- normal
- swelling of the cytoplasm
- condensation of cytoplasm
irreversible changes
- condensation of the nucleus
- fragmentation and dissolution of the nucleus, rupture of the membrane.
Causes of Reversible and Irreversible Injury
Reversible Injury
- Oxygen Deprivation either by hypoxia (insufficient oxygen delivery to tissue) or ischemia (insufficient blood supply
to tissues)
- A thrombus, which is a blood clot that forms in a blood vessel as a result of activation of the coagulation
mechanism.
- An embolus, which is any particulate object that travels in the bloodstream from one site to another. commonly arises from a thrombus but may be composed
of other substances such as bone marrow, fat, air, or cancer tissue.
- Trauma: which disrupts cells by
a direct physical force causing acute injury
- Infection: Damage are primarily produced by inflammatory reaction
- Immune reactions: Includes allergies and autoimmune reactions
Irreversible Injury
NECROSIS:
- Coagulation necrosis: is most commonly caused by anoxia. The coagulation process evolves slowly, over a number of days, collecting cellular material. Recognizable by its pale yellow color and solid but soft texture.
- Liquefaction necrosis is most commonly caused by pyogenic bacteria. This bacteria attracts neutrophils into the area which liquefy the dead tissue. Recognizable by pus (a thick, creamy mixture of dead tissue
and neutrophils) and a hole in the tissue.
- Caseous necrosis is most commonly caused by Mycobacterium tuberculosis, (the bacterium/fungi that causes tuberculosis). Recognizable by its solid, amorphous, cheesy mass.
- Enzymatic fat necrosis occurs following
injury to the pancreas and surrounding adipose tissue as a result of leakage of that organ’s digestive enzymes. recognizable by its chalky, yellow-white nodules somewhat resembling caseous necrosis.
- Gangrenous necrosis (gangrene) is coagulation necrosis with superimposed decomposition by bacteria. Here, only a portion of the body is dead.
APOPTOSIS
- often referred to as “programmed cell death.” Unlike necrosis, it is not
accompanied by any evidence of inflammation.
- Apoptotic cell death is not necessarily an indication of injury. Any cells that have outlived their usefulness are eliminated via apoptosis.
- The most powerful stimulus for apoptosis under pathologic conditions is irreparable damage to DNA by radiation or chemotherapy.
- Acute injury: Sudden and Can rapidly lead to cell death
- Chronic injury: Prolonged in duration
Often mild, but persistent.
true or false?
TRUE
What are the Morphologic features of cell injury first seen at ultrastructural level?
- Mitochondrial swelling
- Breaks in cell membrane
- Dilation of endoplasmic reticulum
what is a defense mechanism that protects the body from injury and promotes repair by:
- bringing fluid, chemicals, and cells to an injured area to limit the extent of injury
- remove necrotic debris
- prepare for the healing
process.
Inflammation
The nature of the inflammatory response is stereotyped;
what does this mean?
it means the degree and duration vary depending on the cause and time course of the injury.
Acute inflammation consists of The vascular and Cellular Phase.
explain the phases.
VASCULAR PHASE
- release of chemical mediators (histamine, kinins, prostaglandins)
- Increases blood flow to the injured area (hyperemia). THIS CAN CAUSE REDNESS
- Increased metabolism CAUSES HEAT
- Increases vascular/capilliary permeability and causes plasma to leak out of cells. THIS CAN CAUSE REDNESS
- the swelling compresses, activating the prostaglandin causing pain
CELLULAR PHASE
- Leukocytes move from blood into tissue at injury site through chemotaxis
Macrophages have two cytokines (IL-1and TNF) that affect the brain (hypothalamus), bone and the liver
explain
The Brain
- IL-1 and TNF stimulates the hypothalamus to release PGE 2 which resets the body temperature ( this is when we develop a fever)= speeds up cut-metabolism to enable a quicker healing process
The Bone
- IL-1 and TNF affects bone marrow to increase the white blood cell production (leukocytosis) = increases Neutrophilsm macrophage that can be mobilised and transported to site of injury.
The liver
- IL-1 and TNF affects the liver = acute phase reactive protein (C -REACTIVE PROTEIN) which can be measured. Increased levels = inflammation happening in the body
enzymes that are initially inactive become activated when 1 enzyme triggers cleavage and activation of another enzyme and so on and so on….this process is known as?
Kinins activate and becomes?
Protease Cascades
- Kinins activate and become bradykinin
Causes increased vascular permeability and pain. - Fibrinogen leaking through permeable vessels activates coagulation.
Fibrin prevents the spread of injury - C5a activates chemotaxis
C5a and C3a increase vascular permability
End Result: Membrane attack complex punches holes in bacterial cell walls
Cytokines Tumor necrosis factor (TNF), IL-1, IL-8, and IL-6:
Increase leukocyte adhesion to endothelium
Increase blood coagulation properties
Stimulate further production of prostaglandins
Elicit fever and neutrophilia
Increase sleep and decrease appetite
IL-10 and transforming growth factor (TGF):
Have a down-regulating effect
Aid resolution of acute inflammation
true or false?
true
Chronic Inflammation can be caused by:
- Acute inflammation that persists because the cause is not completely eliminated
- Non-acute cause present at low level for long time
- Also used as label for histologic picture associated with prolonged inflammation
o Its an Inflammation lasting 2 weeks or longer
true or false?
true
For Chronic Inflammation,
its Typically low grade
Edema and hyperemia less pronounced
Few or no neutrophils present
Area infiltrated predominantly by lymphocytes, plasma cells, and macrophages
Fibrosis is common
true or false?
TRUE
