Cells And tissues Flashcards
How are cells held together in a tissue?
They attach side by side to each other (attached by their lateral domains)
What are the 3 types of cell junctions?
Tight junctions, desmosomes and gap junctions
What is a tight junction?
Where adjacent cells are tightly attached, forming a seal which prevents molecules passing between cells. The plasmalemma of adjacent cells fuse together.
What is a desmosome?
A structure which attaches 2 adjacent cells. Consists of proteins that link the cells. The proteins and intermediate filaments in the cells firmly keep the junction together.
Why are desmosomes found between epithelia cells in the skin?
Desmosomes strengthen connections between cells, preventing stretching and twisting. AS skin cells are under a lot of stress the desmosome helps keep them together.
What are Gap Junctions?
They allow cell communication by having proteins (connexons) forming Channels between cells which allow the movement of ions and molecules.
Where and how do cells attach to the basement membrane?
They attach by their basal domain via hemidesmosomes and focal adhesions
What are the 2 methods of cell death?
Apoptosis and Necrosis
What causes necrosis?
Physical disruption e.g. Injury, toxins or nutrient deprivation
What happens in necrosis?
There is an increase in osmotic pressure so the organelles swell,the chromatin clumps and the cells eventually bursts.
Why does necrosis induce tissue damage and inflammation?
When the cell bursts cytotoxic cellular components spill out
What is apoptosis?
Programmed cell death via molecular signals
How does apoptosis occur?
Deactivating the bcl-2 protein on the mitochondrial matrix initiates apoptosis through enzyme reactions. Enzymes digest shot solid components and the DNA fragments. Cell shrinks into vesicles which are taken up by phagocytes.
What are the 3 specialised types of apical domain?
Microvilli, sterovilli and cilia
What are sterovilli?
Long microvilli found on cells at the epididymis and sensory hair cells in the ear
What are cells with no surface called?
Epitheloid cells
What are the 6 types of cell communication?
Direct contact (gap junctions), autocrine, paraffins, endocrine, synaptic and neurocrine
What is autocrine communication?
Where a cell secretes substances which bind to receptors on the same cell (positive feedback)
What is paracrine communication?
Where cells secrete substances which attach to receptors on neighbouring cells
What is endocrine communication?
Where cells secrete hormones directly into the blood
What are integrins?
Transmembrane proteins which attach the cell to the basement membrane (mechanical function) and allows for the transduction of signals from the extracellular matrix to the cell ( biochemical function).
What are the functions of integrins?
Mechanical, biochemical, used in cell migration and immune patrolling
What are focal adhesions?
Where intercellular actin filaments are anchored to the basement membrane. They play a prominent role in cell movement such as migration of epithelial cells in wound repair
What are hemidesmosomes?
Strong connection between the basement membrane and the basal domain of a cell, held together by integrin proteins.
In which tissues would you find hemidesmosomes?
In the skin and epithelium of the oral cavity (tissue that is subject to abrasion).
