This summary covers basic concepts in pathology that are later used as the building blocks to understand systemic pathological disorders. These building blocks are key to understanding systemic pathology.
ANP Summary 2020
Unit 1. General Pathology
Unit 1.1. Stem cells, cell proliferation and adaption
The different types of stem cells are correctly named
1. Embryonic stem cells
The most undifferentiated type present in the inner cell mass of blastocyst.
• Have virtually limitless cell renewal capacity and can give rise to every cell in the body, hence
being called totipotent
• Under appropriate cell culture conditions, they can form all three germ cell layers, including
neurons, cardiac muscle, liver cells and pancreatic island cells
2. Tissue stem cells (adult stem cells)
Found in intimate association with the differentiated cells of a given tissue, usually in a protective
environment known as a stem cell niche.
• Such niches include the bone marrow (hematopoietic stem cells congregate in a perivascular
niche) whereby soluble factors and other cells within the niches keep stem cells quiescent until
there is a need for expansion and differentiation
• Adult stem cells have a limited ability to differentiate, in that they can only produce cells that
are normal constituents of that tissue
,Define
Proliferation
Rapid increase in the number or amount of cells
Differentiation
The process whereby a cell changes from one type into another
Pluripotent
A cell capable of giving rise to several different types of cells
The different sources of cell signals are correctly named
The sources of signals that most cells respond to can be classified into several groups:
• Pathogens and damage to neighboring cells
Many cells have an innate capacity to sense and respond to damaged cells (danger signals), as well as
foreign invaders such as microbes.
• Cell-cell contacts
These are mediated through adhesion molecules and/or gap junctions
• Cell-ECM contacts
Mediated through integrins
• Secreted molecules
The most important secreted molecules include growth factors, cytokines and hormones (which are
secreted by endocrine organs and act on different cell types)
Signaling pathways also can be classified into different types based on the spatial relationships between
the sending and receiving cells:
• Paracrine
o Cells in the immediate vicinity are affected
o May involve transmembrane sending molecules that activate receptors on adjacent cells
or secreted factors that diffuse for only short distances
• Autocrine
o Occurs when molecules secreted by a cell affect that same cell
o This can serve as a means to entrain groups of cells undergoing synchronous
differentiation during development
, • Synaptic signaling
o Activated neurons secrete neurotransmitters at specialized cell junctions (synapses)
onto target cells
• Endocrine signaling
o A hormone is released into the bloodstream and acts on target cells at a distance
Define (with examples)
• Permanent cells
These are cells that are incapable of regeneration
E.g. Neurons, cardiac cells, skeletal muscle
• Stable cells
These are cells which multiply when needed
E.g. Liver, endocrine glands
• Labile cells
These are cells which are constantly multiplying
E.g. Bone marrow, skin
, The phases of the cell cycle are correctly named
Cell proliferation is fundamental to development, maintenance of steady-state tissue homeostasis and
replacement of dead or damaged cells.
Cell cycle events:
• G1 (pre-synthetic growth)
• S (DNA synthesis)
• G2 (pre-mitotic growth)
• M (Mitotic phase)
• G0 (quiescent state – not actively dividing)
Each stage requires completion of the previous step as well as activation of necessary factors.
The basic functions of the cell cycle checkpoints are correctly described
• Picture above
The major groups of proteins involved in cell cycle control are correctly named and their functions
described
The cell cycle is regulated by numerous activators and inhibitors
• Cyclins
o Named for their cyclic nature of their production and degradation
• Cyclin-dependent kinases
o Acquire the ability to phosphorylate protein substrates by forming complexes with the
relevant cyclins
Transiently increased synthesis of a particular cyclin leads to increased kinase activity of the appropriate
CDK binding partner; as the CDK completes its round of phosphorylation, the associated cyclin is
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