3.7 - 3.9 Integrating cells into tissues Flashcards
What are tissues?
Cells in most multicellualr organisms are arranged into tissues. Tissues are cooperative assemblies of cells and the extracellular matrix
What are organs?
Cooperative assemblies of tissues
What are the 5 major types of tissue?
- Epithelial
- Connective
- Nervous
- Muscle
- Blood and lymphoid tissues
What are the key characteristics of epithelial tissue?
- Cells intimately connected to each other (junctions)
- Apico-basal polarity
- Little extracellular matrix (basement membrane)
What are the key characteristics of connective tissue?
- Cells have few contacts with each other
- No apico-basal polarity
- Large amount of extra cellular matrix
What is nervous tissue?
Specialised, electrochemical signalling
What is muscle tissue?
Specialised, contractile
How are all tissue types seen in an organ such as the gut?

What do the epithelia line?
- External body surfaces
- Internal body cavities
- Tube organs that communicate with exterior (alimentary, genito-urinary and respiratory tracts)
What does the epithelia form?
- Secretory parts of glands and their ducts
- Receptors for centain sensory organs
- Even the brain arises from an epithelium (neuroectoderm) in the embryo
Name these epithelia






What are the functions of the epithelia?
- Protection from mechanical and environmental insults
- Lining of internal tube organs (oviduct and respiratory tracts)
- Example: respiratory epithelium line air conducting tubes to lungs (infection risk)
- Secrete mucus
- Cell specialisation
- Cilia
- Goblet cells





How is a thick keratinised layer produced in the epidermis?
- Epidermis starts as a stem cell on the basal laminar
- Proliferates and differentiate to form keratinocytes that produce keratin and intermediate filaments
- Modified cell death where they lose their nucleus and are just bags of keratin protein

What happens in the respiratory epithelium if there is a genetic defect of cilia?
- Genetic defect of cilia in dynein genes stops them from beating, as dynein are responsible for movement
- Results in primary ciliary dyskinesia
- Situs inversus, male infertility
- Recurrent respiratory disease in children
What happens to the respiratory epithelium if there is a genetic defect of chloride channel?
- Abnormal export from the ER
- Causes cystic fibrosis
- Mucus so thick that cilia can’t move it
What is the function of epithelia in the organs (intestine)?
- Absorption from lumen of organs (intestinal tract and kidney tubules)
- In the intestine there are villi
- Further membrane specialisations in the microvilli (brush border)
- Protect epithelium from acids by secreting mucus

What is the polarity of the gut epithelium which absorbs nutrient molecules?
- It has apico-basal polarity and apical and basal membrane have different properties
- Apical has active transport channel where there is increased glucose concentration in the cell
- Basal has passive channel and transporter protein for diffusion of glucose to the blood
- There are special cell-cell junctions that prevent backflow of molecules

How do the apical and basal membranes differ?
- Apical is for absorption, secretion, specialisations (microvilli and cilia)
- Basal is for adhesion to extracellular matrix and secretion into sub mucosa

What are the four different types of junctions for epithelial cells?
- Tight junctions
- Adherens junctions (desmosomes)
- Gap juncitons
- Focal contacts (hemidesmosomes)
How are cell junctions in epithelial cells usually aranged?
- Cells may have more than one type of junction
- Arranged in junctional complexes









































































