Intro to cells, tissues and organs Flashcards
What is a cell?
Fundamental units of life, capable of independent existence
Differences between prokaryotic and eukaryotic cells
Pro: smaller, no nuclear envelope, no nucleoli, no histones, few intracellular membranes, 60-70S ribosomes
Euk: larger, prominent nuclear envelope, nucleoli present, DNA complexed with histones, many membrane bound organelles, 70-80S ribosomes
Properties of cells
Irritability - react to environment Conductivity Contractility Absorption and assimilation Excretion and secretion Respiration Growth Reproduction
From cells to systems
Cells -> simple tissue -> compound tissue -> organ -> system
What is a tissue?
An assemblage of cellular and extra cellular elements in which one or more types of cell or fibre usually predominates to form material basis of one of the functional systems of the body
How do tissues arise?
Zygote -> morula -> blastocyst 1st then 2nd week -> conceptus with 3 germ layers developing
Derivatives of the Primary germ layers
Ectoderm
Endoderm
Mesoderm
What are the primary tissues
- Epithelia
- Connective tissues
- Nervous tissues
- Muscular tissues
Epithelia
Sheets of closely-packed cells derived from one of 3 germ layers
Cover or line the surface of an organ
Sheets: simple or compound/stratified
Connective tissues
Cells derived from mesoderm
Produce extra cellular matrix of fibres and ground substance
Nervous tissue
Develop from neuro-ectoderm
Consist of cells which mainly possess processes called neuritis which conduct impulses when stimulated
Muscular tissues
Derived from mesoderm
Composed of cells (multinucleated syncytia) whose cytoplasm contains filaments made of contractile proteins
Secretion
Cells take up and release molecules to the environment without compromising its integrity
Endocytosis and exocytosis
Endocytosis
Inwards
- Invagination: fusogenic proteins
- Adherence
- Fusion
Exocytosis
Outwards
- Apposition
- Adherence: fusogenic proteins
- Fusion
