Connective Tissue and Skin Flashcards
What two things is the extracellular matrix made up of?
Ground substance (hyaluronate proteoglycan aggregates) Fibres (collagen, reticular, elastic)
What are the two components of connective tissue?
Cells and extra cellular matrix
Name the two types of embryonic connective tissue
Mesenchyme
Mucous connective tissue
What is the amino acid sequence of collagen
Glycine-X-Y
Give the structure of collagen
Three alpha helix chains wrapped around eachother
What type of collagen is in found in hyaline and elastic cartilage?
Type II
Which connective tissue does Marfan’s syndrome affect?
Elastic tissue
What type of inheritance is Marfan’s?
Autosomal dominant
What type of connective tissue is the dermis?
Dense irregular
How does the arrangement of collagen make skin more resistant to tearing
Bundles of collagen are densely packed but irregularly arranged so that they are orientated in different directions
How are tendons arranged?
Collagen bundles lie in a parallel, densely packed formation in a line. Rows of elongated fibroblasts lie between the bundles.
What do fibroblasts do?
Synthesis and secrete ground substance and the fibres that lie within the ground substance.
Give three fibres that make up connective tissue
Collagen, elastin, reticular
Name the four layers of the epidermis
Stratum corneum, granular layer, prickle cell layer, basal layer
In which layer of the epidermis does keratinocytes mitosis mostly occur?
Basal layer
In which layer do the keratinocyte daughter cells lose their ability to divide?
Prickle cell layer
What do keratinocytes synthesise?
Keratins
What happens to keratinocytes in the granular layer of the epidermis?
Lose their plasma membrane
Differentiate into corneocytes, the main cells of the stratum corneum
Which layer of the epidermis contains keratohyalin granules?
Granular layer
What are keratohyalin granules made up of?
Aggregations of keratins, other fibrous proteins, enzymes which degrade the phospholipid bilayer and cross-link proteins including fillagrin and involucrin.
What type of cells is the stratum corneum made up of?
Flattened corneocytes
What is the transit time of a keratinocyte from the basal layer to the stratum corneum?
30-40 days
In which layer of the epidermis are Langerhans cells found?
Prickle cell layer
What do Langerhans cells in the epidermis do?
Present antigens to T lymphocytes
Mediate immune reactions
What is psoriasis?
Abnormal epidermal growth and differentiation
What is vitiligo?
Autoimmune destruction of melanocytes.
Where are melanocytes found?
The basal layer of the epidermis
What is connective tissue?
Cells, fibres and ground substance which has a number of functions including joining together other tissues, supporting the body and its structures, and providing protection for underlying organs.
What is the structure of a proteoglycan monomer?
A core protein with about 100 glycosaminoglycan (GAG) units attached.
What charge do GAGs have and what does this do?
Negative
Attract water to form a hydrated gel
Where can type I collagen be found?
In the skin dermis, tendons and capsules of organs.
What is reticulin?
Type III collagen
Where is reticulin found?
Forms fibrils around nerve and muscle cells and within lymphatic tissues and organs.
Where are elastic fibres found?
Artery walls and dermis
What do macrophages do?
Phagocytic - can degrade foreign organisms and cell debris
Professional antigen presenting cells (present foreign material to T lymphocytes of the immune system)
What do mast cells do?
Become coated with Immunoglobulin E. When IgE binds cross links with an allergen, contents of granules in the mast cells are released. Granules contain heparin, histamine, substances that attract eosinophils and neutrophils.
Describe the process of keratinocyte differentiation
Keratinocyte mitosis occurs in the basal layer
Daughter keratinocytes move up to form the prickle cell layer.
Terminal differentiation begins and they lose their ability to divide
Keratinocytes synthesis keratins, which contribute to the strength of the epidermis.
In the granular layer, keratinocytes lose their plasma membrane and begin differentiating into corneocytes, the main cells of the stratum corneum.
What does the granular layer contain? (Detail!)
Keratohyalin granules which are aggregations of
- keratins
- other fibrous proteins
- enzymes which degrade the phospholipid bilayer and cross link proteins
What is allergic contact dermatitis?
Mediated by Langerhans cells
What is malignant melanoma?
Malignant growth of melanocytes
Give the main components of the dermis
Extracellular matrix of collagen (mostly type 1) and elastin Blood vessels Lymphatic vessels Mast cells Nerves
What do scars mainly comprise of?
Collagen
What are the four main functions of the skin?
Barrier
Sensation
Thermoregulation
Psychosexual communication
What four things can a loss of barrier function lead to?
Loss of fluids Loss of protein Loss of other nutrients Loss of heat Excessive absorption of potentially harmful exogenous agents
List some macroscopic variations in the skin
Hairiness Thickness Oiliness Laxity Colour
