CONNECTIVE TISSUES
[Note — Wheater prefers the term ‘supporting tissues’ to reflect the wide range of
important functions, but this is not yet generally accepted.]
Objectives
a) To be able to state the general functions of connective tissues.
b) To be able to state the names and properties of the principal fibre and cell types
of CT.
c) To be able to outline the role of the matrix in conferring differing properties of CT.
d) To be able to give the basis of the morphological classification of CT.
e) To be able to relate structure to function of the different types of CT.
f) To recognise the inter-relatedness of all CT cells.
——————
Connective tissue (CT) occurs everywhere in the body in a variety of
forms. Its principal function is support, both structural and
physiological. It is both a skeletal framework for tissues and also the
route through which blood vessels and nerves run. CT binds organs as
in fascia and capsules of organs, and supports the other components of
organs e.g. interlobular CT of glands and the lamina propria of epithelia.
CT has an important function in modulating the differentiation and
division of the overlying cells.
Histologically, CT is characterised by having cells scattered within
varying amounts of extracellular material, which consists of fibres and
ground substance (matrix).
1. Components of Connective Tissues
a) Fibres — collagenous, reticular or elastic.
b) Cells — of many types, including white blood cells which have
left the blood vessels. Macrophages and fibroblasts are the
commonest cell types. The cells are derived from a common
precursor (ancestral) cell which is closely related to the
precursor of blood cells. (See Figure 2.)
d) Ground substance — typically amorphous, may be sol/gel and is
mainly composed of hyaluronic acid and glycoproteins
(especially chondroitin sulphate). To a very large extent it is the
properties of the different glycoproteins which determine the
different properties of connective tissues. The types and
arrangement of the glycoproteins varies within connective
tissues and according to age.
9
In addition to Connective Tissue Proper there are the
Specialised Connective Tissues: Blood, Cartilage, Bone and the
Lymphoid organs (see below).
2. Classification of Connective Tissue Proper
a) Proportion of fibres (low — Loose; high — Dense). In practice,
there is a graded series of density.
b) Arrangement of fibres — Regular (in parallel bundles) or
Irregular (in a coarse feltwork).
3. Types of Connective Tissue Proper
3.1 Loose Connective Tissues
a) Loose (Areolar) Connective Tissue. Develops from
mesenchyme. It occurs as packing and support of most
structures (e.g. lamina propria underlying epithelia). Has all
types of fibre with collagen the most conspicuous. Reticular
fibres may be abundant at the edges of other structures. The
unstained ground-substance occurs in patches (areolae).
Areolar CT is well-supplied with nerves and blood vessels
which supply the overlying epithelium. Macrophages and
fibroblasts are the predominant cell types.
c) White Adipose Tissue (WAT). Fat cells are the main cell type
and are surrounded by reticular fibres. Because fat is dissolved
out in by the alcohols used in histological preparation, the cells
normally appear empty with a thin ring of cytoplasm. Note
that Brown Adipose Tissue (BAT) has many small lipid
droplets, in contrast to the single droplet in WAT. Adipose
tissue is highly vascular reflecting the dynamic state of rapid
metabolism and turnover of lipid.
e) Reticular tissue. 'Primitive', composed of probably pluripotent
cells and reticular fibres. Found only in lymphoid tissues.
Other principal cell types: lymphoid cells, eosinophils and mast cells.
3.2 Dense Connective Tissues
Characterised by having a relatively high proportion of fibres.
a) Dense Irregular Connective Tissue. A coarse feltwork of mainly collagenous
fibres forming sheets. Designed to withstand multidirectional stress.
b) Dense Regular Connective Tissue. Parallel fibres to withstand unidirectional
stress. Fibroblasts are the predominant cell type. The predominant fibre
type is collagen, except in special elastic ligaments.
Examples. Tendons and ligaments, where the collagen fibres are arranged
into bundles or fascicles.
เนื้อเยื่อเกี่ยวพัน[หมายเหตุ — คำ 'สนับสนุนเนื้อเยื่อ' ต้อง Wheater ถึงมากมายฟังก์ชั่นที่สำคัญ แต่นี้ไม่ได้โดยทั่วไปยอมรับ]วัตถุประสงค์ก) เพื่อสามารถระบุฟังก์ชันทั่วไปของเนื้อเยื่อเกี่ยวพันขเพื่อให้สามารถระบุชื่อและคุณสมบัติของชนิดเส้นใยและเซลล์เป็นหลักของกะรัตc) สามารถร่างบทบาทของเมทริกซ์ใน conferring คุณสมบัติแตกต่างกันของกะรัตd) เพื่อให้สามารถให้ข้อมูลพื้นฐานของการจัดประเภทของของกะรัตอี) เพื่อให้สามารถเชื่อมโยงโครงสร้างฟังก์ชันที่แตกต่างของกะรัตf) จะรู้ relatedness ระหว่างเซลล์ CT ทั้งหมด——————เนื้อเยื่อเกี่ยวพัน (CT) ที่เกิดขึ้นในทุกหนทุกแห่งในร่างกายในหลากหลายแบบฟอร์มการ หน้าที่หลักคือ สนับสนุน ทั้งโครงสร้าง และสรีรวิทยา มีทั้งกรอบอีกในเนื้อเยื่อและการเส้นทางผ่านที่หลอดเลือดและเส้นประสาททำงาน CT binds อวัยวะเป็นรับทั้งการบำบัดและแคปซูลของอวัยวะ และส่วนประกอบอื่น ๆ ของสนับสนุนอวัยวะเช่น interlobular CT ของต่อมและ propria lamina ของ epitheliaCT มีฟังก์ชั่นสำคัญในการเกี่ยวที่สร้างความแตกต่าง และส่วนของเซลล์อยู่เหนือกว่าHistologically, CT เป็นโรค โดยมีเซลล์กระจายอยู่ภายในจำนวนวัสดุ extracellular ซึ่งประกอบด้วยเส้นใยที่แตกต่างกัน และสารดิน (เมทริกซ์)1. ส่วนประกอบของเนื้อเยื่อเกี่ยวพันก) ใย — collagenous, reticular หรือยืดหยุ่นb) Cells — of many types, including white blood cells which haveleft the blood vessels. Macrophages and fibroblasts are thecommonest cell types. The cells are derived from a commonprecursor (ancestral) cell which is closely related to theprecursor of blood cells. (See Figure 2.)d) Ground substance — typically amorphous, may be sol/gel and ismainly composed of hyaluronic acid and glycoproteins(especially chondroitin sulphate). To a very large extent it is theproperties of the different glycoproteins which determine thedifferent properties of connective tissues. The types andarrangement of the glycoproteins varies within connectivetissues and according to age.9In addition to Connective Tissue Proper there are theSpecialised Connective Tissues: Blood, Cartilage, Bone and theLymphoid organs (see below).2. Classification of Connective Tissue Propera) Proportion of fibres (low — Loose; high — Dense). In practice,there is a graded series of density.b) Arrangement of fibres — Regular (in parallel bundles) orIrregular (in a coarse feltwork).3. Types of Connective Tissue Proper3.1 Loose Connective Tissuesa) Loose (Areolar) Connective Tissue. Develops frommesenchyme. It occurs as packing and support of moststructures (e.g. lamina propria underlying epithelia). Has alltypes of fibre with collagen the most conspicuous. Reticularfibres may be abundant at the edges of other structures. Theunstained ground-substance occurs in patches (areolae).Areolar CT is well-supplied with nerves and blood vesselswhich supply the overlying epithelium. Macrophages andfibroblasts are the predominant cell types.c) White Adipose Tissue (WAT). Fat cells are the main cell typeand are surrounded by reticular fibres. Because fat is dissolvedout in by the alcohols used in histological preparation, the cellsnormally appear empty with a thin ring of cytoplasm. Notethat Brown Adipose Tissue (BAT) has many small lipiddroplets, in contrast to the single droplet in WAT. Adiposetissue is highly vascular reflecting the dynamic state of rapidmetabolism and turnover of lipid.e) Reticular tissue. 'Primitive', composed of probably pluripotentcells and reticular fibres. Found only in lymphoid tissues.Other principal cell types: lymphoid cells, eosinophils and mast cells.3.2 Dense Connective TissuesCharacterised by having a relatively high proportion of fibres.a) Dense Irregular Connective Tissue. A coarse feltwork of mainly collagenousfibres forming sheets. Designed to withstand multidirectional stress.b) Dense Regular Connective Tissue. Parallel fibres to withstand unidirectionalstress. Fibroblasts are the predominant cell type. The predominant fibretype is collagen, except in special elastic ligaments.Examples. Tendons and ligaments, where the collagen fibres are arrangedinto bundles or fascicles.
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