Coverings And Tissue Of The Body Flashcards
Define cell.
Basic unit of living organism
Define simple tissue.
Collection of similar cells
Define compound tissue.
Mix of cell + ECM
Define organ.
Distinct group of several tissues in a living organism that have been adapted to perform a specific function
Define system.
Group of organs with distinct role
What embryological layers are epithelial coverings derived from?
Mainly ectoderm
Endoderm
What is a free surface of epithelium?
Surface not attached to other cells
What is epithelium?
Thin tissue forming outer layer of a body’s surface, lining the alimentary canal+ other hollow structures as well as the inner surfaces of cavities in many internal organs
What is endothelium?
Tissue which forms a single layer of cells lining various organs + cavities of the body especially blood vessels, heart + lymphatic vessels formed from embryonic mesoderm i.e. blood vessel epithelium
What is mesothelium?
Tissue that lines the pleurae, peritoneum + pericardium but derived from surface layer of embryonic mesoderm i.e. epithelium of body cavities
What is serosa?
Tissue of a serous membrane
What does epithelial tissue cover?
Body surfaces inside + outside e.g. line many body cavities & exterior of digestive/respiratory tract, heart + blood vessels
Form glands derived developmentally
What are the functions of epithelial tissue?
- Protection
- Barrier
- Permit passage of substances
- Secrete substances
- Absorb substances
What happens if the epithelia is damaged?
Associated with a wide range of clinical problems e.g. foot ulcers
What layers of skin exist?
Epithelium (innermost)
Basement membrane
Dermis (outermost)
What is the dermis?
Thick layer of fibrous + elastic tissue made mostly of collage + a small amount of elastin
Also contains nerve endings, sweat glands, oil (sebaceous glands), hair follicles + blood vessels
What is the basement membrane?
Connective tissue region for cell attachment; acts a selective barrier (can change in disease states)
How are epithelium normally named?
Based on cellular arrangement, shape + specializations
What types of layers can epithelium have?
Simple
Stratified
What different shapes can epithelium have?
Flat (squamous)
Square (cuboid)
Rectangular (columnar)
What different specialisations can epithelium have?
Microvilli Villi Cilia Mucoid glands (goblet cells) Keratin
What is the main role of simple squamous epithelia? Where are they found?
Small intracellular volume as they are flattened cells -> permit exchange so main role is diffusion
Blood/lymphatic capillaries, alveoli, thin LOH but also for filtration in Bowmans capsule + secretion/absorption as serous fluid
What are the main features of simple cuboidal epithelium? What is their role?
Larger IC volume so used for absorption/production of things
Where are simple cuboidal epithelium found?
Choroid plexus (produce CSF) Kidney tubules Glands/ducts of glands Terminal bronchioles of lungs (if ciliated) Surface of ovaries Inside lining of eyes
What are the main features of simple columnar epithelium? What is their role?
Large IC volumes so potential for energy reserves + high organelle density
Roles in motility, absorption + processing
Where can simple columnar epithelium be found?
Stomach SI LI Uterus + tubes Glands/ducts of glands Bronchioles of lungs Auditory tubes Bile duct Gallbladder Ependyma
What are the main features of pseudo-stratified epithelium?
Appear stratified due to nuclei sitting at different levels but all cells contact BM
Where are pseudo-stratified epithelium found?
Larynx Nasal cavity Paranasal sinuses Nasopharynx Auditory tubes Trachea Bronchi Male urethra Salivary gland ducts
Why do stratified squamous epithelium have multiple layers?
Well adapted for role in protection because if outer cells are damaged, they are replaced by cells from deeper layers so a continuous barrier of epithelial cells is maintained in tissue so found in areas prone to abrasion/friction
Where are stratified squamous epithelium found?
Skin Corneas Mouth Throat Epiglottis Larynx Oesophagus Anus Vagina Lower urethra Sebaceous gland ducts
Where does the villi specialisation tend to be found most in the body?
In SI for absorption
Where does the goblet cell specialisation tend to be found most in the body?
GI tract
Respiratory tract
Where is the keratinized outer layer found?
Skin
What are the main features of transitional epithelium?
Stretchy + waterproof so permit cell distention allowing it to return to original shape
Where are transitional epithelium found?
Urinary bladder
Ureter
Superior urethra
What is the difference between cilia and microvilli?
Cilia have a microtubule core so actively move whereas microvilli do not actively move
What is the function of cilia?
Move materials across free surface of cell e.g. mucus in respiratory tract containing foreign particles is moved out of airways via these
What is the function of microvilli?
Non-motile + containing microfilaments that greatly increase SA so occur in cells that absorb/secrete e.g. serous membranes + lining of SI
The structure of tissue and epithelia change with role. Give a couple of examples of this.
Trachea: pseudostratified with cilia + goblet cells, SM walls + hyaline cartilage support -> provide air passage, get rid of foreign bodies + secrete mucus
Alveoli: simple squamous epithelium, elastic tissue + capillaries in between -> diffusion of O2/CO2 between lungs + blood
Define gland.
A collection of epithelial cells that secrete substances
What are the 2 types of glands?
- Tubular: simple or coiled
2. Acinar: simple branched or compound branched
What is an acinus?
Small sac-like cavity in a gland surrounded by secretory cells
What are some glands coiled/branched?
Increase SA allowing them to secrete into a lot of different areas
What controls glandular tissue?
The endocrine system: regulates activity in the body by secreting hormones into blood via these glands
What are exocrine and endocrine glands?
Exocrine: glands with ducts lined with epithelium e.g. sweat + salivary glands
Endocrine: extensive blood vessels + cellular products are hormones secreted into blood + carried through body e.g. pituitary gland
What are epithelial cancers called?
Carcinomas
What keeps the epithelium together in a healthy individual?
Tight/occluding junctions firmly bind/glue cells together + provide a permeability barrier
What do anchoring junctions do?
Unite cell cytoskeletal proteins + EC structures riveting cells + their internal skeleton together
What do gap junctions do?
Permit functional coupling + rapid intercell communication via connexons that joins 2 cells together via passage of low MW molecules
In what types of tissues would you want gap junctions? Why?
Nerves
Heart
SM
Because cells in these tissues must communicate in a quick + efficient way
What is connective tissue?
Tissue that connects, supports, binds or separates other tissues or organs typically having relatively few cells embedded in a amorphous matric with collagen + other fibres including cartilaginous, fatty + elastic tissues - contains large amounts of ECM + forms structural framework of body tissues
What is the function of connective tissue?
Enclose/separate other tissues Connect tissues to eachother Support/move parts of body Store compounds Cushion/insulation Transport Protection
What are the 3 different cell types that secrete products that form extracellular tissue components?
- Chrondrocytes: form cartilage
2 Fibroblasts: forms tendon + ligaments - Osteoblasts/osteocytes: form + maintain bone
What cells are found in connective tissue?
Fibroblasts (form fibrous tissue) Chondroblasts (form cartilage) Osteoblasts (form bone) Osteocytes (maintain bone) Osteoclasts (break bone down) Adipocytes Mast cells Macrophages Platelets Undifferentiated mesenchymal cells
What are the 2 classes of macromolecule that contribute to the extracellular matrix?
- Fibrous proteins e.g. collagen
2. Polysaccharides e.g. GAGs
What mainly allows the production of multiple tissue types?
Variation in the amount, type, composition + arrangement of macromolecules
What are the features of collagen?
Highly organised + unbranched
Ligaments + tendons
High tensile strength
What are the features of elastin?
Organised branches fibres
Arteries + vertebral column ligaments
Elastic properties
What are the features of reticulin?
Loosely arranged primitive collagen in lymphatic nodes, liver + spleen
What are glycosaminoglycans (GAGs)?
Polysaccharide chains that attract H2O (natural moisture factors) so found in skin + form centre of intervertebral disc
Why do organs show regional variation in their structure?
Because each organ performs a different function so the cell types + structures needed within them is going to vary
