Connective tissues and skin (rest look at Callum's ESA1 Flashcards
What are some of the various functions of connective tissues?
- Structural - links together muscle, nerves and epithelium
- Metabolic support - medium for diffusion of nutrients and waste
- Physiological support - protection against infection and aid in injury repair
Name a liquid connective tissue with gas transport and immune defence functions
Blood
Name solid connective tissues with protective, mobility and structural functions
Cartilage and bone
What makes up the ground substance?
Hyaluronate proteoglycan aggregates
Where can a mucous connective tissue be found?
Umbilical cord
Name the three types of regular connective tissue
- Loose (areolar) connective tissue
- Dense connective tissue
(i) regular
(ii) irregular
List some specialised connective tissues
Adipose tissue Blood Cartilage Bone Lymphatic tissue Haemopoietic tissue
Mesenchyme (embryonic connective tissue) is pluripotent and differentiates into which rise to which connective tissue cells (as well as serous membranes, vascular and urogenital systems and to muscle)?
Chrondroblasts -> cartilage
Lipoblasts -> fat cells
Fibroblasts -> ligament, tendon, capsules, general supporting tissues
Osteoblasts -> bone
(Myoblasts -> skeletal muscle (not a connective tissue)
Mesenchymal cells in the adult that persist, have what function?
Can give rise to new connective tissue when healing is required
What shape are mesenchymal cells?
Spindle shaped
What makes up the structure of hyaluronate proteoglycan aggregates?
Linear aggregates of hyaluronic acid (itself a GAG) with attached proteoglcyan monomers (core protein to which ca100 GAG units attach
How do GAGs contribute to the hydration of the ground substance?
They have a high density of negative charge which attracts water, forming a hydrated gel
Where is type 1 collagen found?
Tendons, capsules of organs and skin dermis
Where is type 2 collagen (elastin) found?
Hyaline and elastic cartilage
Where is type 3 collagen (reticulin) found?
Around muscle and nerve cells and within lymphatic tissues and organs
Why does collagen type 1 fibril have periodic banding?
Because each fibril is composed of staggered collagen molecules
Describe the structure of type 1 collagen
Every third aa of the alpha-chain is glycine
Collagen molecule = Triple helix of alpha chains
Each fibril is composed of staggered collagen molecules
What banding pattern do type 1 collagen make?
68nm repeat
What do elastic fibres consist of?
Primarily elastin, which enfold and are surrounded by microfibrils of fibrillin
What are the clinical signs of Marfan’s syndrome?
Abnormally tall
Exhibit arachnodactyly (long and slender fingers and toes)
Frequent joint dislocation
Risk of aortic rupture
What is the inheritance pattern of Marfan’s syndrome?
Autosomal dominant disorder causing abnormal expression of the fibrillin gene
In an artery what makes up the tunica intima?
Endothelial cells
What type of collagen fibre makes up the tunica media of arteries?
Elastic fibres (type 2 collagen)
What type of collagen fibre makes up the tunica adventitia of arteries?
Collagen (type 1)
What type of cell produces the elastin, collagen and matrix in the tunica media?
Smooth muscle cells
Why does dermis contain elastic fibres and irregularly orientated densely packed bundles of collagen?
Elastic fibres -> stretch and restore shape after bent/folded
Multiple orientation -> resist forces in multiple directions and therefore shearing
What type of connective tissue makes up capsules of organs?
Varies from loose to dense connective tissue
Describe the cell ultrastructure of a fibroblast
Abundant rER - synthesising and glycosylating proteins
Abundant secretory vesicles
What do mast cells look like under the microscope?
Abundant granules which can obscure the nucleus when stained with basic dyes
Where are mast cells found?
Connective tissue near blood vessels but NOT in the CNS (to avoid damaging effects of oedema there)
What do mast cell granules contain?
- Heparin - anti-coagulant
- Histamine - increases blood vessel wall permeability
- Cytokines that attract eosinophils and neutrophils
How are mast cells activated, releasing their granules?
When IgE molecules on their surface are cross-linked by binding to an allergen
Name the two types of embryonic connective tissue
Mesenchyme and Mucous connective tissue
What is the difference in the development of white and brown adipocytes?
Both are derived from mesencymal tissue which differentiates into early lipblasts, which develop numerous lipid droplets in their cytoplasm. In white adipose tissues these multiple droplets fuse into a single large droplet which displaces all other cell contents to the periphery. In brown adipose tissue these multiple lipid droplets remain separate and have a central nucleus
In typical H&E stained, wax-embedded preparations of adipose tissue why do cells appear white and empty?
The toluene and xylene used for tissue preparation has dissolved away the lipid
Where is brown adipose tissue found in the adult and newborn?
Newborn - sternum, scapula and axillae
Adult -chest and neck
Why is brown adipose tissue brown?
Due to its rich vascular supply and abundant mitochondria. It has a high respiratory capacity for the generation of heat.
What is a distinctive feature of neutrophils under the miscroscope?
One nucleus, but looks like 5. In females can have a stick poking out (inactivated X chromosome)
What is a major underlying cause of skin ageing and wrinkling?
UV-induced injury to dermal collagen and elastin. This is called ‘solar elastosis’
List two skin cancers
Malignant melanoma
Basal cell carcinoma - relatively benign if dealt with quickly but can eat away all the surface of your face
Why does hair turn grey?
Some melanocytes stopping functioning in hair follicles (this does not happen in the epidermis)
What is the cause of ‘port wine stain’ birth marks?
Congential malformation of dermal blood vessels -> increase in number of dermal capillaries and vasodilation
What does the pilosebaceous unit contain?
hair follicles
sebaceous glands
smooth erectopilus muscle
What are three causes of acne?
- Abnormal differentiation of sebaceous gland ducts
- Increased sebum production
- Infection with normally harmless skin bacteria
These changes in SGs normally occur at puberty
Where are sebaceous glands most abundant?
On the face. The typical site of acne
What is hyperhidrosis?
Increased sweating the cause of which is normally unknown. May affect only the palms and soles
What can disrupted skin barrier (e.g. in extensive psoriasis) lead to?
Loss of fluid -> moist skin Loss of protein Loss of other nutrients Loss of heat (vasodilation) Excessive absorption of potentially harmful exogenous agents, especially drugs
