The Tissues of the Human Body: Connective Tissue

Question 1

Features of connective tissues

Answer 1

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)

Question 2

Features of connective tissues

Answer 2

Like Epithelia

CT is supplied by nerves
Exception: cartilage

Question 3

Connective tissue (CT) is composed of

Answer 3

Extracellular matrix细胞外基质 (ECM) and CELLS

Question 4

Connective Tissue Extracellular Matrix is composed of

Answer 4

Ground Substance (GS)in association with Protein Fibres (3 major types in different proportions

Question 5

Connective Tissue Extracellular Matrix

Answer 5

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.

Question 6

Connective Tissue Extracellular Matrix

Answer 6

cartilage: ECM is firm and rubbery, but in bone hard and inflexible.

Question 7

Connective Tissue Extracellular Matrix

Ground Substance

Answer 7

Ground substance is composed of a mixture of :

Water
Proteins (gelatine in jelly!)
Polysaccharides(sugars)

Question 8

There are 3 different types of connective tissue fibres in the extracellular matrix (ECM):

Answer 8

Collagen fibres(thick)
Reticular fibres
Elastic fibres

Question 9

Collagen fibres(thick)

Answer 9

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

Question 10

Reticular fibres

Answer 10

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

Question 11

Elastic fibres

Answer 11

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.

Question 12

Two Common Connective Tissue Cell Types

Answer 12

Fibroblasts

Adipocytes(fat cells)

Question 13

Fibroblasts

Answer 13

Location

Widely distributed in connective tissues; migratory

Question 14

Fibroblasts

Answer 14

Function

Secrete components of the matrix (fibres and ground substance)

Question 15

Adipocytes(fat cells)

Answer 15

Location

Under the skin and around organs

Question 16

Adipocytes(fat cells)

Answer 16

Function

Store fat (triglycerides)

Question 17

Classification of Connective Tissue:

Answer 17

Embryonic

Mature

Question 18

Embryonic Connective Tissues

Answer 18

Type

Mesenchyme (embryonic)
Mucous

Question 19

Mature Connective Tissues

Answer 19

Loose
Dense
Blood
Lymph
Cartilage
Bone

Question 20

Loose connective tissues

疏松结缔组织

Answer 20

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

Question 21

Dense connective tissues

致密结缔组织

Answer 21

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

Question 22

Supporting connective tissues: Cartilage

The dense network of collagen and elastic fibres

Answer 22

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.

Question 23

Supporting CT: Bone or osseous tissue 骨或骨组织

Answer 23

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)).

Question 24

Compact bone密质骨

Answer 24

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

Question 25

Spongy bone

Answer 25

Porous多孔渗水的 inner bone tissue that lies underneath the compact bone.Also known as Cancellous bone松质骨

Question 26

Bone or osseous tissue

Answer 26

Bones are composed of several connective tissue types, including bone tissue(which is either compact or spongy)

Question 27

Compact bone

Answer 27

Compact contains osteons. Stores calcium & phosphorous. Protection & support.

Question 28

Spongy bone

Answer 28

Lacks osteons, stores triglycerides (yellow marrow骨髓) and produces blood cells(red marrow).

Question 29

Bone cells Four cell types are found in bone.

Answer 29

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 ```

Question 30

The Structure of Osteons骨的结构 (Haversian Systems)

Answer 30

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

Question 31

Bone cells Four cell types are found in bone.

Answer 31

Osteoclasts reabsorb dead bone Osteoblasts lay down new bone Osteoclasts remodel new bone Chondroblasts lay down hyaline cartilage callus

Question 32

Liquid Connective Tissue Blood

Answer 32

Consists of blood plasma(a liquid extracellular matrix) and formed elements(red cells, white cells and platelets)

Question 33

“Formed elements” of blood

Answer 33

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

Question 34

Connective tissue is composed of......

Answer 34

Connective tissue is composed of cells and the matrix between them

Question 35

Ground Substance 基质

Answer 35

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.

Question 36

Some Terminology

Answer 36

• 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 ```

Question 37

Glycosaminoglycans (GAGS) | 葡糖氨基葡聚糖；[有化] 粘多糖

Answer 37

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

Question 38

Applications of GAGS

Answer 38

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.

Question 39

Application of GAGS as part of ground substance

Answer 39

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

Question 40

Abnormal Periorbital ECM and thyroid disease(Exophthalmos)（眼球突出） 眼眶周围ECM异常与甲状腺疾病

Answer 40

•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

Question 41

Abnormal Periorbital ECM and thyroid disease (Exophthalmos)

Answer 41

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

Question 42

Marfan Syndrome 马凡综合征

Answer 42

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).