The Tissues of the Human Body: Connective Tissue Flashcards
Features of connective tissues
Unlike epithelia
CT is NOT found on body surfaces
(think of where bones, cartilage, blood is located)
CT can be highly vascular血管的
(Exceptions: cartilage软骨 which is avascular无血管的 and tendons肌腱 with very little blood supply)
Features of connective tissues
Like Epithelia
CT is supplied by nerves
Exception: cartilage
Connective tissue (CT) is composed of
Extracellular matrix细胞外基质 (ECM) and CELLS
Connective Tissue Extracellular Matrix is composed of
Ground Substance (GS)in association with Protein Fibres (3 major types in different proportions
Connective Tissue Extracellular Matrix
The protein fibres of the ECM are secreted by the cells in the ECM.
The structure of the ECM largely dictates the connective tissue qualities.
Connective Tissue Extracellular Matrix
cartilage: ECM is firm and rubbery, but in bone hard and inflexible.
Connective Tissue Extracellular Matrix
Ground Substance
Ground substance is composed of a mixture of :
Water
Proteins (gelatine in jelly!)
Polysaccharides(sugars)
There are 3 different types of connective tissue fibres in the extracellular matrix (ECM):
Collagen fibres(thick)
Reticular fibres
Elastic fibres
Collagen fibres(thick)
1) Very strong but flexible to resist pulling forces
2) Features vary in different tissues e.g. more water around collagen in cartilage than in bone.
3) Collagen 25% of your body and is the most abundant protein!
4) Common in bone, cartilages, tendons and ligaments
5) Parallel bundles
Reticular fibres
1) Composed of collagen with a coating of glycoprotein.
2) Collagen in fine bundles with a coating of glycoprotein(more protein than sugar)
3) Made by fibroblasts
4) Provide strength and support.
5) Form part of the basement membrane
6) Thinner, branching - spreads through tissue.
7) Form networks in vessels and through tissues especially adipose tissue, nerve fibres, smooth muscle tissues
Elastic fibres
1) Thinner than collagen fibres
2) Fibrous network
3) Consist of the protein elastin surrounded by the glycoprotein fibrillin to give more strength and stability.
4) Can be stretched 150% without breaking.
5) Found in skin, blood vessels and lung.
Two Common Connective Tissue Cell Types
Fibroblasts
Adipocytes(fat cells)
Fibroblasts
Location
Widely distributed in connective tissues; migratory
Fibroblasts
Function
Secrete components of the matrix (fibres and ground substance)
Adipocytes(fat cells)
Location
Under the skin and around organs
Adipocytes(fat cells)
Function
Store fat (triglycerides)
Classification of Connective Tissue:
Embryonic
Mature
Embryonic Connective Tissues
Type
Mesenchyme (embryonic)
Mucous
Mature Connective Tissues
Loose Dense Blood Lymph Cartilage Bone
Loose connective tissues
疏松结缔组织
Areolar Connective Tissue网形结缔组织
Adipose Connective Tissue脂肪结缔组织
Reticular connective Tissue网状结缔组织
Dense connective tissues
致密结缔组织
Dense Regular Connective Tissue
Tendons 肌腱(muscle to bone);
Ligaments 韧带(bone to bone);
aponeuroses 腱膜 (muscle to muscle).
Dense Irregular and dense elastic tissues
Supporting connective tissues: Cartilage
The dense network of collagen and elastic fibres
Hyaline Cartilage透明软骨
e.g. anterior ends of ribs; respiratory cartilage –nose, trachea, bronchi.
The nasal septum ends of long bones.
Flexibility and movement.
Supporting CT: Bone or osseous tissue 骨或骨组织
Bones are organs composed of several connective tissue types, including bone tissue(which is either compact紧凑的 or spongy轻软的 (BM)).
Compact bone密质骨
The outer layer of bone and forms the shaft of long bones.
It is also known as cortical bone皮质骨.
Compact bone is composed of many rod-shaped units known as either Osteons or Haversian systems骨或哈弗氏系统
Spongy bone
Porous多孔渗水的 inner bone tissue that lies underneath the compact bone.Also known as Cancellous bone松质骨
Bone or osseous tissue
Bones are composed of several connective tissue types, including bone tissue(which is either compact or spongy)
Compact bone
Compact contains osteons.
Stores calcium & phosphorous. Protection & support.
Spongy bone
Lacks osteons, stores triglycerides (yellow marrow骨髓) and produces blood cells(red marrow).
Bone cells
Four cell types are found in bone.
Osteogenic cells生骨细胞
that develop, starts to lay down collagen; become trapped and become osteoblasts.
Osteoblasts造骨细胞
bone-forming cells. Lay down more collagen, mineralization process starts.
Osteocytes骨细胞
mature bone cells derived from osteoblasts trapped within the extracellular matrix. Maintain bone tissue. Involved in the exchange of nutrients and wastes. Have gap junctions.
Osteoclasts破骨细胞 Large, •Multinucleated cells •Formed from the fusion of blood monocytes 单核细胞 Break-down bone
The Structure of Osteons骨的结构 (Haversian Systems)
The basic unit of compact bone is the osteon, with four parts:
1.Lamellae.骨板
concentric rings of mineral salts for hardness (e.g. calcium phosphate and calcium hydroxide, which together form hydroxyapatite) and collagen(for tensile strength).
2.Lacunae:裂陷
small spaces between lamellae that contain mature bone cells (osteocytes)
3.Canaliculi:微管
“minute canals” (containing EC fluid and minute osteocytic processes) that radiate from lacunae and provide routes for oxygen, nutrients and waste.
4.Central (Haversian) canal:
blood, lymph and nerves
Bone cells
Four cell types are found in bone.
Osteoclasts reabsorb dead bone
Osteoblasts lay down new bone
Osteoclasts remodel new bone
Chondroblasts lay down hyaline cartilage callus
Liquid Connective Tissue
Blood
Consists of blood plasma(a liquid extracellular matrix) and formed elements(red cells, white cells and platelets)
“Formed elements” of blood
Erythrocytes红细胞 transport oxygen and carbon dioxide
Leukocytes白血球 combat disease:
Neutrophils中性粒细胞 and monocytes单核细胞(macrophages)are phagocytic吞噬细胞, engulfing吞噬 bacteria.
Platelets血小板(from megakaryocytes巨核细胞 in red marrow): clotting凝血
Connective tissue is composed of……
Connective tissue is composed of cells and the matrix between them
Ground Substance 基质
Ground substance is composed of a mixture of :
- Water
- Proteins (gelatine in jelly!)
- Polysaccharides多糖(sugars)
The sugars include Glycosaminoglycans粘多糖(GAGS or mucopolysaccharides黏多糖).
GAGS join with core proteins to form proteoglycans蛋白聚糖.
Some Terminology
• Proteoglycans
– Comprise Protein + Glycosaminoglycan (GAG)
• Glycosaminoglycans (GAGS) – Another name “mucopolysaccharides” – Long unbranched polysaccharides – Repeating disaccharide unit • Amino sugar e.g.: N acetylglucosamine • Uronic sugar e.g. glucuronic acid • Highly polar and attract water
Glycosaminoglycans (GAGS)
葡糖氨基葡聚糖；[有化] 粘多糖
Sulphated硫酸化 GAG examples:
- Dermatansulphate皮肤素硫酸盐
- Heparin sulphate 硫酸肝素
- Keratan sulphate 硫酸角质素
- Chondroitin sulphate 硫酸软骨素
These bind to proteins to form proteoglycans蛋白聚糖 (PGs)
Non-sulphated GAG example:
• Hyaluronic acid透明质酸
•Hyaluronic acid does not bind directly to the protein backbone but is joined to various PGs
Applications of GAGS
Hyaluronic Acid透明质酸:
viscous粘性的 slippery湿滑的 substance binds cells together, lubricates润滑 joints and maintains维护 the shape of the eyeball
Hyaluronidase透明质酸酶:
- produced by white blood cells, sperm and some bacteria.
- This makes the ground substance more liquid so they can move more easily in it or makes access to the egg easier for sperm.
Application of GAGS as part of ground substance
Chondroitin Sulphate硫酸软骨素: support and provide the adhesive features of cartilage软骨, bone, skin, blood vessels.
Keratan Sulphate硫酸角质素: found in bone, cartilage, the cornea角膜 of the eye
Dermatan Sulphate硫酸肤质素: found in skin, tendons, blood vessels, heart valves心脏瓣膜
Abnormal Periorbital ECM and thyroid disease(Exophthalmos)（眼球突出）
眼眶周围ECM异常与甲状腺疾病
•Most common in younger women
•Goitre (swollen thyroid gland)
•Autoimmune over-activation of the thyroid (goitre)
甲状腺自身免疫过度激活
•Autoimmune action on fibroblasts 纤维母细胞 in ECM of the eye (exophthalmos眼球突出)
对眼外基质成纤维细胞的自身免疫作用
Abnormal Periorbital ECM and thyroid disease (Exophthalmos)
The deposition of glycosaminoglycans and the influx of water increase the orbital contents.
糖胺聚糖的沉积和水的流入增加了眼眶的含量
Marfan Syndrome 马凡综合征
A hereditary defect in elastic fibres usually resulting from a dominant mutation in a gene on chromosome 15, which codes for fibrillin原纤蛋白.
Fibrillin is a large glycoprotein糖蛋白 (350 kDa) that contributes to a structural scaffold脚手架 for elastin弹性蛋白.
The body produces growth factor Transforming Growth Factor beta(TGFb)– increases growth because does not bind normally to fibrillin to keep it inactive (theory).
