TOB S5 - Connective Tissues and Skin (connective done with MMF lecture - use Callum's too)

Question 1

What are the functions of connective tissue?

Answer 1

1. 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

Question 2

What are the components of connective tissues?

Answer 2

1. Cells 2. Extracellular matrix (separates cells): - Ground substance (hyaluronate proteoglycan aggregates) - Fibres (collagen, reticular, elastic)

Question 3

How do connective tissues differ?

Answer 3

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

Question 4

What is connective tissue?

Answer 4

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

Question 5

Classify embryonic connective tissues

Answer 5

• Mesenchyme - Mucous connective tissue

Question 6

Classify connective tissue proper (or regular connective tissue)

Answer 6

• Loose (or areolar) connective tissue - Dense connective tissue - regular or irregular

Question 7

Classify different types of specialised connective tissue

Answer 7

• Adipose tissue - Blood - Cartilage - Bone - Lymphatic tissue - Haemopoietic tissue

Question 8

What cells are derived from mesenchyme cells?

Answer 8

See image

Question 9

What are the common cell types in connective tissue?

Answer 9

• 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

Question 10

What does the extracellular matrix consist of?

Answer 10

• 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

Question 11

Classification of connective tissues: mesenchyme

Answer 11

Cells: spindle-shaped, large nuclei Extracellular materials: reticular fibres and small blood vessels Examples: Embryonic origin

Question 12

Classification of connective tissues: Mucous CT (Whaton’s jelly)

Answer 12

Cells: fibroblasts, oval nuclei Extracellular materials: collagen bundles, irregular Examples: umbilical cord

Question 13

Classification of connective tissue: loose CT

Answer 13

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

Question 14

Classification of connective tissues: dense irregular CT

Answer 14

Cells: fibroblasts, macrophages Extracellular materials: thick wavy bundles of collagen, elastic and reticular fibres Examples: dermis

Question 15

Classification of connective tissues: dense regular CT

Answer 15

Cells: parallel rows of flattened fibroblasts Extracellular materials: parallel rows of densely packed collagen Examples: tendons, ligaments

Question 16

Classification of connective tissues: reticular CT

Answer 16

Cells: reticular cells, large oval nuclei, lymphocytes, macrophages Extracellular matrix: reticular fibres Examples: liver, kidney, spleen, lymph nodes, bone marrow

Question 17

What are the variations in macroscopic structure of the skin?

Answer 17

• Hair: site, sex, age, ethnicity - Colour: ethnicity, site, UV exposure - Laxity: wrinkling - Oiliness - thickness

Question 18

What is the overall structure of the skin?

Answer 18

Epidermis, dermis and hypodermis - microscopic structure See image

Question 19

What are the layers of the epidermis?

Answer 19

Outside to in: Stratum corneum (major role in skin barrier function), granular layer, prickle cell layer, basal cell layer (keratinocyte mitosis mainly occurs here)

Question 20

What are keratinocytes?

Answer 20

Synthesise keratins which contribute to strength of epidermis

Question 21

Describe keratinocyte differentiation

Answer 21

• 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

Question 22

What are corneocytes?

Answer 22

Main cells of stratum corneum

Question 23

What are the other cells of the epidermis?

Answer 23

• Melanocytes - Langerhans cells

Question 24

Describe melanocytes

Answer 24

• Dendritic cells with neural crest origin, intervals along basal layer, produce melanin - In darker skin: more melanin production not more melanocytes

Question 25

Describe Langerhans cells

Answer 25

• 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

Question 26

What is the dermo-epidermal junction?

Answer 26

• Between epidermal basement membrane and dermis - Best seen with PAS

Question 27

Describe the dermis

Answer 27

• Dense irregular connective tissue - Fibroblasts (synthesise extracellular matrix) - Extracellular matrix (collagens, elastin) - Blood vessels - Lymphatic vessels - Mast cells - Nerves

Question 28

Describe patterns of blood vessels in skin

Answer 28

• 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

Question 29

Describe skin appendages

Answer 29

• Hair follicles and sebaceous glands (branched, acinar/holocrine secretion) - Sweat glands (eccrine and apocrine) - Nails

Question 30

What are the functions of the skin?

Answer 30

• 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)

Question 31

Describe thermoregulatory eccrine sweating for maintenance of body temperature

Answer 31

• Evaporation of eccrine sweat causes cooling - Very important in maintenance of body temp

Question 32

What are the main diseases of the skin?

Answer 32

• Psoriasis - Vitilgo - Alopecia areata - Malignancies (basal cell carcinoma, squamous cell carcinoma, malignant melanoma)

Question 33

What is psoriasis?

Answer 33

Patchy lesions on skin from increased proliferation of keratinocyte (look up different types in lecture)

Question 34

What is vitiligo?

Answer 34

Patches of white due to lack of pigmentation

Question 35

What is alopecia areata?

Answer 35

Autoimmune attack on hair follicles

Question 36

What are different types of malignancies?

Answer 36

• Basal cell carcinoma - Squamous cell carcinoma - Malignant melanoma

Question 37

What are the four types of collagen?

Answer 37

Type 1 - dermis, tendons

Type 2 - H & E cartilage

Type 3 - reticular fibres

Type 4 - basal lamina of basement membrane