Flashcards in TOB S5 - Connective Tissues and Skin Deck (108):
What is the embryonic origin of connective tissues?
What are the three basic components of connective tissue?
Amorphous ground substance
What are the basic functions of connective tissues?
Filling spaces between organs
Forming tendons and ligaments
What are the Resident cell types in connective tissues?
Macrophages aka. Tissue histocytes
What are the Visitant cell types in connective tissues?
What is the function of fibroblasts/cytes in connective tissues?
Synthesise and maintain extracellular matrix (Including collagen, elastic fibres, reticular fibres and ground substance)
Fibrocytes are more mature and less active fibroblasts.
What is the function of Mesenchymal cells in connective tissues?
Undifferentiated cells that differentiate into other cells and maintain extracellualar materials
What is the function of macrophages in connective tissues?
Ingest foreign material (bacteria, dead cells, cell debris)
What type of cells are macrophages derived from?
Give the specific names of monocytes found in:
Liver - Kupfer cells
CNS - Microglia
Bone - Osteoclasts
What is the function of mast cells in connective tissues?
Give 2 examples of molecules found in these cells.
Congregate near blood vessels and release pharmacologically active molecules
Eg Heparin, Histamine found in granules in the cell
What is the function of adipocytes in connective tissues?
Found in small clusters or aggregates, they store lipids and act as a insulator and shock absorber (cushioning organs and joints).
What is the function and derivation of leukocytes in connective tissues?
Derived from blood cells, responsible for production of immunocompetent cells
How does composition of connective tissue determine function?
The constituents of the extracellular matrix define whether the tissue is a loose packing tissue or of primary mechanical importance
What are the three fibres found in connective tissue's extracellular matrix?
In what form does collagen occur in connective tissues?
Where does collagen synthesis occur?
Occurs in bundles of non-elastic fibres of variable thickness
RER of cells
What is the most common type of collagen?
Describe the composition and form of Reticular fibres
Made up of type three collagen.
Forms thin branching fibres that form delicate networks around certain structures
Around what structures might a network of reticular fibres be found?
Blood vessels, adipocytes, smooth muscle cells, nerve fibres, certain epithelial cells
Around what organs do reticular fibres form a structural framework/supporting mesh?
Describe the structure and function of Elastic fibres
Highly elastic fibres containing amorphous protein and elastin surrounded by fibrillin
Can stretch up to 150% restin length due to high lysine content
Describe the structure and function of the amorphous ground substance in connective tissue
Gel like matrix in which fibres and cells are imbedded. Tissue fluid diffuses through it.
Composed of Glycosaminoglycans (GAGs), Proteoglycans and glycoproteins.
Where is loose connective tissue found in organs?
Forms the septa (walls) and trabeculae (rods) that make up the framework inside organs
How might loose connective tissue become distended?
During Oedema distended by Extracellular fluid (ECF)
Describe the composition of mucous connective tissue (Wharton's Jelly)
Where it might be found?
Large stellate fibroblasts (that will often fuse with similar adjacent cells)
Few macrophages and lymphocytes present
Ground substance has high concentration of Hyaluronic acid and a network of fine collagen fibres
Only found in Umbilical cord and Subdermal connective tissue of the embryo
Where might Areolar connective tissue be found?
Deep under the skin
Below mesothelium of peritoneum
Associated with adventitia of blood vessels
Surrounding parenchyma of glands
In terms of loose connective tisse what are the distinguishing features of areolar connective tissue
Contains fibroblasts and macrophages as well as some mast cells
Collagen fibres abundant but elastin fibres also present.
In terms of Loose connective tissue what is unique about the structure of Adipose tissue?
Loose connective tissue with adipocytes occuring singularly or in groups between collagen fibres
Adipocytes make up the majority of cells
What are the 4 common types of Loose connective tissue?
Mucous connective tissue
How does the structure of Dense connective tissue vary from loose connective tissue?
Closely packed fibres
Less ground substance
What is the defining feature of dense regular connective tissue and how does this relate to function?
Where is dense regular CT found?
Fibres oriented in parallel to provide maximum tensile strength
Tendons, Aponeuroses (flattened tendons) and Ligaments
How does fibre arrangement in ligaments differ from tendons?
Collagen fibres in ligaments less regularly arranged
In what types of Dense regular connective tissue can fibroblasts be found?
All of them
What is an elastic ligament?
A ligament where most fibres are elastin
What is a fascicle in a tendon?
A bundle of collagen and fibroblasts
Where does Loose connective tissue occur in tendons?
Endotendineum (layers of LCT interspersed through collagen)
Peritendineum (outer layer of LCT around tendon)
What surrounds tendons?
A fibrous sheath
Describe the structure of Dense irregular connective tissue and relate this to function
Collagen fibres criss cross in many directions to counteract multidirectional forces to which the tissue is subjected.
Mostly collagen with some elastic and reticular fibres
Where might Dense irregular connective tissue be found?
Deep fascia of muscles
Dermis of skin
Capsules, large septa and trabeculae of many organs
What causes Systemic Sclerosis and what does it cause?
Excessive accumulation of collagen (fibrosis) in all organs
Causes hardening and functional impairment
What is a keloid scar and why do they form?
Scars on the skin caused by abnormal amounts of collagen
What is the result of vitamin C deficiency?
Defective collagen synthesis leading to degeneration of connective tissue.
Peridontal ligament is highly affected due to high collagen turnover
Loosening of teeth in their sockets with subsequent loss.
What causes Marfan's syndrome and what is a major effect of this?
Genetic defect in gene coding for fibrillin leading to undeveloped elastic fibres.
Large elastic arteries (eg. Aorta) can rupture due to weakened connective tissue.
What is the result of Ethlers-Danos disease?
Deficiency of type 3 collagen causing ruptures in tissue with high reticulin content.
What macroscopic features of skin are subject to variation?
What reasons are behind variations in skin colour?
What reasons are behind variation in skin hair?
Site (Armpit vs Palm)
Sex (Facial and more profuse body hair in men)
Age (baldness in men, greying in both sexes)
Ethnicity (colour, character)
What are the reason/s behind variation in skin thickness?
Site (scalp vs ball of foot)
What factors affect skin laxity/wrinkling?
What factors might affect skin oiliness?
How does variation in skin colour influence presentation of vitiligo?
Much less of a problem in fair skinned as it is barely visible.
How does variation in skin colour influence susceptibility to skin damage or skin cancer?
Fair skinned more susceptible to:
UV induced acute sunburn
What is the type of cell found in the epidermis?
Stratified squamous keratinised epithelium made up mainly of keratinocytes
What are the four layers of the epidermis?
Give in descending order.
Horny layer(stratum corneum)
Granular layer(stratum granulosum)
Prickle cell layer(stratum spinosum)
Basal layer(stratum basale)
Describe the processes of keratinocyte mitosis and differentiation
Keratinocytes from the stratum basale move upwards after undergoing mitotic division to form the stratum spinosum, where terminal differentiation begins
They then lose their ability to divide
What do keratinocytes produce?
What are the functions of keratins in the skin?
Contribute to strength of epidermis
Main constituent to hairs and nails
Describe the molecular structure of keratins.
Heterodimeric fibrous proteins
What changes to keratinocytes occur as they move into the granular layer?
Lose their plasma membrane
Begin differentiating into corneocytes (main cells of the stratum corneum)
Apart from cells, what is another component of the stratum granulosum?
What is the composition of keratohyalin granules?
Other fibrous proteins (eg Filaggrin, involucrin)
Enzymes which degrade the phospholipid bilayer of cells
Crosslink proteins (eg Filaggrin, involucrin)
What are the functions of filaggrin and involucrin?
Filaggrin: Aggregates keratins
Involucrin: Forms a major part of corneocyte envelope
What type do cells make up the stratum corneum?
What is the function of the stratum corneum?
Made up of layers of flattened corneocytes
Major function is as a barrier (resists abrasion etc)
What is the transit time from stratum basale to stratum corneum for a cell?
What are melanocytes, what is their embryonic origin and where are they found?
Dendritic cells of neural crest origin
What is the function of melanocytes?
How does ethnicity effect their function?
Produces more melanin in darker skin
What are Langerhans cells and where are they found?
Dendritic cells of bone marrow origin
Scattered throughout stratum spinosum
What is the function of Langerhans cells?
Present antibodies to T lymphocytes
Mediate immune reactions (Eg allergic contact dermatitis)
What is significant about the staining properties of melanocytes and Langerhans cells?
Difficult to see without special stains
Where is the dermo-epidermal junction and what does it consist of?
Just below the stratum basale
What stain is used to best see the dermo-epidermal junction?
What are the constituents of the Dermis layer of skin?
Fibroblasts and extracellular matrix
What is the function of fibroblasts in the dermis?
Synthesise the extracellular matrix
What does the extracellular matrix of the dermis contain?
Collagens (especially type 1)
Other extracellular matrix components
What is the main component of scar tissue?
What is the result of excessive scar tissue production following wounding?
Describe the form and distribution of blood vessels in the dermis?
Small blood vessels in the more superficial dermis
(Mainly capillaries, some small venules and arterioles)
Larger blood vessels in the deeper dermis
How do birthmarks arise?
Congenital malformation of dermis blood vessels
Where are mast cells found in the dermis?
Distributed around blood vessels
What is the major significant secretory product of mast cells in the dermis?
What is the result of histamine release from mast cells in the dermis?
Increased vascular permeability leading to plasma leakage into dermis.
This results in localised oedema that causes urticaria (hives) and angio-oedema in the skin.
What is the function of nerves in the dermis?
Sensory nerves transmit sensation
Name the various skin appendages found in the dermis
Hair follicles and sebaceous glands (Pilosebaceous unit)
Immediate subcutaneous fat (adipose tissue)
What type of glands are sebaceous glands and what type of secretion do they utilise?
What is the clinical significance of the sebaceous duct in a Pilosebaceous unit?
Acne obstructs flow of secretions through this duct onto hair
What are the two types of sweat glands?
What is the function of Eccrine sweat glands?
Where are they found?
How are they controlled?
Major sweat glands found in most areas of the body
Produce a clear, odourless secretion of water and NaCl (NaCl reabsorbed in duct to reduce salt loss)
Active in thermoregulation
Controlled by the hypothalamus
Describe the composition of an Eccrine sweat gland
Intra-epidermal spiral duct
Straight dermal portion of duct
Coiled acinar secretory portion in the dermis
Where are Apocrine sweat glands most abundant?
What is the function of Apocrine sweat glands?
Produce odourless, protein rich secretions
This function is of no discernible value
How is body odour produced?
Digestion of protein rich secretions from Apocrine sweat glands by cutaneous microbes
What are the main functions of the skin?
Describe the barrier function of the skin.
How is this relevant to drug administration?
Give an example of a disease that might disrupt the barrier function.
Stratum corneum forms a major barrier preventing percutaneous absorption of exogenous substrates
The barrier must be overcome during percutaneous absorption of drugs
Barrier may be seriously disrupted by Psoriasis.
Describe the Sensory function of the skin.
Sensory nerves of the skin allow a sense of:
Tissue damage (Pain)
Give two examples of diseases that affect the sensory function of the skin.
Leprosy - Disease of the peripheral nerves
Diabetic sensory neuropathy
What are the two methods of thermoregulation employed by the skin
Thermoregulatory eccrine sweating
What are the twin processes involved in vascular thermoregulation and the consequences of each?
Dilation of skin blood vessels:
Leads to heat loss
Leads to pallor and heat conservation
How is eccrine sweating involved in thermoregulation?
Evaporation of eccrine sweat leads to cooling
How is the skin involved in psychosexual communication?
Appearance manipulated as a means of communication or expression (Eg Tattoos and piercings)
Describe the how Psoriasis leads to it's characteristic scaled appearance
Extreme proliferation of stratum basale cells Causing gross thickening of Stratum spinosum and excessive stratum corneum production
Hence leading to the characteristic excess scaling of the skin
What proportion of the population experiences Psoriasis in their lives?
What is the cause of Psoriasis?
Exact cause not known
However, it runs in families and so is influenced by genetic factors.
What cells are associated with a malignant melanoma?
Tumour of melanocytes
How is the dermo-epidermal junction significant to maligant melanoma prognosis?
Superficial spreading melanoma doesn't penetrate the basement membrane and is associated with a good prognosis
More penetrating 'nodular' melanomas are associated with a very poor prognosis
What makes malignant melanomas hard to spot in a clinical environment?
The look like moles (benign growths of melanocytes)
What is Alopecia areata?
An autoimmune attack on hair follicles causing hair loss
What is Vitiligo?
An autoimmune disease in which the immune system attacks melanocytes causing areas of de-pigmentation