TOB S5 - Connective Tissues and Skin (connective done with MMF lecture - use Callum's too) Flashcards
What are the functions of connective tissue?
- Provide substance and form to the body and organs 2. Provide a medium for diffusion of nutrients and organs 3. Attach muscle to bone and bone to bone 4. Provide a cushion between tissues and organs 5. Defend against infection 6. Aid in injury repair
What are the components of connective tissues?
- Cells 2. Extracellular matrix (separates cells): - Ground substance (hyaluronate proteoglycan aggregates) - Fibres (collagen, reticular, elastic)
How do connective tissues differ?
In terms of: - The types of cells which they contain - The abundance/density of their cells - The constitution of their extracellular matrix in terms of: ground substance composition, fibre type, abundance and arrangement
What is connective tissue?
Forms a huge continuum throughout the body, linking together muscle, nerve and epithelial tissue in a structural way but also providing support in metabolic and physiological ways
Classify embryonic connective tissues
- Mesenchyme - Mucous connective tissue
Classify connective tissue proper (or regular connective tissue)
- Loose (or areolar) connective tissue - Dense connective tissue - regular or irregular
Classify different types of specialised connective tissue
- Adipose tissue - Blood - Cartilage - Bone - Lymphatic tissue - Haemopoietic tissue
What cells are derived from mesenchyme cells?
See image
What are the common cell types in connective tissue?
- Fibroblasts: ground substance, collagen, elastic and reticular fibre - Macrophages: phagocytosis, Ag presenting cell, release cytokines - Mast cells: Histamine, Heparin - Adipose: White-stores lipids. Brown: generates heat - Leukocytes
What does the extracellular matrix consist of?
- Ground substance- Gel-like matrix, glycosaminoglycan units (proteoglycan structure), glycoproteins - Collagen- Type 1: dermis, tendons. Type 2: Hyaline and Elastic cartilage. Type 3: reticular fibres. Type 4: basal lamina of basal membrane - Elastic fibres - Extracellular fluid
Classification of connective tissues: mesenchyme
Cells: spindle-shaped, large nuclei Extracellular materials: reticular fibres and small blood vessels Examples: Embryonic origin
Classification of connective tissues: Mucous CT (Whaton’s jelly)
Cells: fibroblasts, oval nuclei Extracellular materials: collagen bundles, irregular Examples: umbilical cord
Classification of connective tissue: loose CT
Cells: fibroblasts, macrophages, mast cells, fat cells, plasma cells Extracellular materials: ribbon-like collagen fibres, elastic fibres, watery ground substance Examples: adipose, blood, areolar CT
Classification of connective tissues: dense irregular CT
Cells: fibroblasts, macrophages Extracellular materials: thick wavy bundles of collagen, elastic and reticular fibres Examples: dermis
Classification of connective tissues: dense regular CT
Cells: parallel rows of flattened fibroblasts Extracellular materials: parallel rows of densely packed collagen Examples: tendons, ligaments
Classification of connective tissues: reticular CT
Cells: reticular cells, large oval nuclei, lymphocytes, macrophages Extracellular matrix: reticular fibres Examples: liver, kidney, spleen, lymph nodes, bone marrow
What are the variations in macroscopic structure of the skin?
- Hair: site, sex, age, ethnicity - Colour: ethnicity, site, UV exposure - Laxity: wrinkling - Oiliness - thickness
What is the overall structure of the skin?
Epidermis, dermis and hypodermis - microscopic structure See image
What are the layers of the epidermis?
Outside to in: Stratum corneum (major role in skin barrier function), granular layer, prickle cell layer, basal cell layer (keratinocyte mitosis mainly occurs here)
What are keratinocytes?
Synthesise keratins which contribute to strength of epidermis
Describe keratinocyte differentiation
- Basal layer: keratinocyte mitosis - prickle cell layer: lose ability to divide and produce keratins - Granular layer: lose plasma membrane and start to become corneocytes, contains keratin and enzymes) - Stratum corneum: dead, flattened corneocytes Transit time keratinocyte from basal layer to stratum corneum is 30-40 days
What are corneocytes?
Main cells of stratum corneum
What are the other cells of the epidermis?
- Melanocytes - Langerhans cells
Describe melanocytes
- Dendritic cells with neural crest origin, intervals along basal layer, produce melanin - In darker skin: more melanin production not more melanocytes
Describe Langerhans cells
- Dendritic cells with bone marrow origin - Scattered in prickle cell layer - Mediate immune reactions and present antigens to T lymphocytes - Difficult to see without special stains
What is the dermo-epidermal junction?
- Between epidermal basement membrane and dermis - Best seen with PAS
Describe the dermis
- Dense irregular connective tissue - Fibroblasts (synthesise extracellular matrix) - Extracellular matrix (collagens, elastin) - Blood vessels - Lymphatic vessels - Mast cells - Nerves
Describe patterns of blood vessels in skin
- Smaller blood vessels in superficial dermis (mainly capillaries, small venules and arterioles) - Leads to interconnecting vessels - Leads to larger blood vessels in the deeper dermis
Describe skin appendages
- Hair follicles and sebaceous glands (branched, acinar/holocrine secretion) - Sweat glands (eccrine and apocrine) - Nails
What are the functions of the skin?
- Barrier function - (outer epidermis: stratum corneum major barrier preventing per cutaneous absorption of exogenous substance) - Prevents water loss - Sensation (affected by leprosy, diabetic sensory neuropathy) - Thermoregulation (vascular regulation and thermoregulatory eccrine sweating for maintenance of body temp) - Psychosexual communication (manipulation)
Describe thermoregulatory eccrine sweating for maintenance of body temperature
- Evaporation of eccrine sweat causes cooling - Very important in maintenance of body temp
What are the main diseases of the skin?
- Psoriasis - Vitilgo - Alopecia areata - Malignancies (basal cell carcinoma, squamous cell carcinoma, malignant melanoma)
What is psoriasis?
Patchy lesions on skin from increased proliferation of keratinocyte (look up different types in lecture)
What is vitiligo?
Patches of white due to lack of pigmentation
What is alopecia areata?
Autoimmune attack on hair follicles
What are different types of malignancies?
- Basal cell carcinoma - Squamous cell carcinoma - Malignant melanoma
What are the four types of collagen?
Type 1 - dermis, tendons
Type 2 - H & E cartilage
Type 3 - reticular fibres
Type 4 - basal lamina of basement membrane
