Medical Biology Lecture 15,16: Specialized Connective Tissues PDF

Medical Biology- Lecture 15,16 SpecializedFirst Connective Tissues stage Lecturer / Zahraa Ch. Hameed Learning Objectives: Types of cartilages Describe the components of all types. Understand the location and functions of all cartilages types. Understand the general features of bone. Describe the...

Medical Biology- Lecture 15,16 SpecializedFirst Connective Tissues stage Lecturer / Zahraa Ch. Hameed Learning Objectives: Types of cartilages Describe the components of all types. Understand the location and functions of all cartilages types. Understand the general features of bone. Describe the adipose tissue. • • Define the blood tissue. Classification of blood tissue. Specialized Connective Tissue This type of tissue is with rigid material for modified to support (bone and cartilage) or with fluid intracellular substance for transportation (blood). Support tissues Cartilag e Hyalin e Elasti c Hemopoieti c Bloo d Red blood cells Bone Fibr o Compac t Spong y White blood cells Platelets Cartilage consists of two basic components:1. Cells (5%) 2. Extracellular matrix (95%) • Cells of cartilage are called chondrocytes. • Cartilage is avascular tissue that receives its nutrition by diffusion from adjacent tissues. - The surfaces of most cartilage structures are surrounded by a wellvascularized dense irregular connective tissue membrane called a perichondrium (except fibrocartilages) from which the nutrients diffuse through the matrix to the chondrocytes. - Chondroblasts:-the predominant cell type in growing cartilage. - Chondrocytes:- or mature cartilage cells are typically found in small groups within common cavities called LACUNAE - Based on composition and mechanical properties of matrix, cartilages are classified into three types: 1. Hyaline cartilage 2. Elastic cartilage 3. Fibrocartilage 1. Hyaline Cartilage Histologically, hyaline cartilage consists of cells (chondrocytes), ground substance, and fibers. ● Appearance : bluish-white, translucent. ● Locations: Nasal septum, tracheal rings, articular cartilages, costal cartilages, and fetal skeleton. ● Composition : ● ● Chondrocytes : spherical in shape, at the periphery elliptic - appear in groups - up to 8 cells originating by mitotic division of a single chondrocyte – isogenous group - housed in matrix cavities- lacunae (in living tissue fill the lacunae, shrinking during preparation) Extracellular matrix (glassy ): cells are surrounded by basophilic matrix territorial (capsular) matrix (rich in acidic glycosaminoglycans) and interterritorial matrix – smooth, paler, less basophilic (collagen II - does not form fibres, fibrilles interact with proteoglycan aggregates, are not visible by LM because their refractive index is similar to that of ground substance and are masked by the glycosaminoglycans; hence the matrix appears homogeneus and smooth) Flowchart 1: Histology of hyaline cartilage Fig1: Photomicrograph. Hyaline cartilage. Fig. 2: Histology of hyaline cartilage (practice figure). Fig. 3: Hyaline cartilage: Matrix and lacunae (practice figure). Functions • Hyaline cartilages maintain patency of trachea and the main bronchi because of the firmness. • Because of flexibility, costal cartilages provide support and protection to thoracic viscera. • Articular cartilages provide smooth surface for the movements. ● ● ● ● ● 2. Elastic Cartilage Elastic cartilage contains ground substance, fibers, and cells (chondrocytes). Elastic cartilage is surrounded by perichondrium. Appearance : yellowish color. Locations: Pinna of external ear, external acoustic meatus, auditory tube, epiglottis, tips of arytenoids, and corniculate and cuneiform cartilages of larynx. Composition : Chondrocytes : similar to hyaline cartilage, housed in lacuna singly or in pairs (coffee bean) Extracellular matrix : fibrils of collagen II and network of fine elastic fibers (are arranged in more or less regular fashion between the cells), less amount of ground amorphous substance On the surface - perichondrium is identifiable. Functions Elastic cartilage provides elasticity, resilience, and firmness to the structure. Flowchart 2: Histology of elastic cartilage Fig. 4: Histology of elastic cartilage (practice figure). Fig. 8.6: Photomicrograph. Elastic cartilage (low magnification on left and high magnification on right, H&E stain). 3. Fibrocartilage fibrocartilage shows rows of chondrocytes embedded in matrix bundles of thick collagen fibers. ● ● ● ● ● Appearance : characteristics between dense connective tissue and cartilage . Locations: Intervertebral discs, menisci of knee joint, and pubic symphysis. Composition : Chondrocytes : small, spindle-shaped, similar to fibroblasts arranged singly or in long rows Extracellular matrix : great number of collagen I fibers acidophilic, amorphous matrix less abundant . - Perichondrium is not identifiable. Functions • Fibrocartilage helps in shock absorption. • Fibrocartilage helps to withstand compression and shearing forces. Flowchart 8.3: Histology of fibrocartilage Fig. 8.7: Histology of white fibrocartilage. Bone tissue:Bone is the specialized type of connective tissue that has extracellular matrix containing calcium salts. it consists of cells and matrix. Mineralized extracellular matrix provides hardness to bones. Bone also performs hematopoietic function (production of blood cells). General features of bone • Long bone has two ends (epiphysis) that are connected by long shaft (diaphysis). • On cross-section, long bone shows diaphysis, epiphyses, and coverings (endosteum and periosteum). Diaphysis/Shaft • It is a tubular sheath covering a central cavity called marrow cavity. • Tubular sheath does not have visible spaces. This type of bone is called compact bone. Epiphyses • Ends of long bone show a thin layer of compact bone covering a meshwork of bony plates. • Cavities of the bone are called bone marrow. • Bone marrows are of the following two types: – Red bone marrow: It is red in color and performs hematopoietic functions. – Yellow bone marrow: With advancing age (in adult), red bone marrow from shafts of long bones get replaced with adipose (fat) tissue (yellow in color). - Bones are classified to their shapes to: long bones (limbs), short bones (ankle), flat bones (skull), irregular bones (sphenoid). Under the microscope, bones are classified to spongy bone and compact bone. Covering of Bone • Bone has an outer surface and internal surface that faces marrow cavity. These surfaces have the following coverings: Periosteum: • Periosteum is a layer of connective tissue that covers external surface of bone except at two places: 1. At muscle attachment. 2. At area covered by articular cartilage. • Periosteum has two layers: Outer fibrous and inner cellular (osteogenic) layers. Endosteum : (thinner than periosteumhas) only a single layer of osteoprogenitor cells. Bone is a specialized type of connective tissue. It consists of three basic components as follows: 1. Cells 2. Fibers 3. Ground substance Bone tissue:1-Compact bone ➢ ➢ ➢ ➢ ➢ it is harder, much denser,, stronger and stiffer than spongy bone. It contributes about 80% of the weight of a human skeleton. The primary anatomical and fundamental functional unit of compact bone is the osteon or haversian system. Each osteon consists of layers of lamellae that surround a central canal (haversian canal), the haversian canal contains the bone's blood vessels supplies and continuity between the haversian canal of adjacent osteon is achieved by (Volkman,s canal), the lamellae are arranged parallel to the surface, each osteocyte within its own lacuna. Osteocytes make contact with the cytoplasmic processes of their counterparts via a network of small transverse canals called canaliculi. This network facilitates the exchange of nutrients and metabolic waste. Longitudinal section of dry, compact bone Osteocytes in lacunae (structure of bone). 2-Spongy bone (Cancellous) ➢ More porous that is located internally . ➢ It has a higher surface-area-to-mass ratio than compact bone because it is less dense. This makes it softer, and weaker but more flexible. ➢ Highly vascular and frequently contains red bone marrow where haematopoiesis. ➢ The primary anatomical and functional unit of spongy bone is the trabeculae, it is a series of branching, overlapping plates of matrix, within these, interconnecting cave like spaces and these spaces function well in storage bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells and white blood cells, they also function in weight reduction. Cancellous bone with trabeculae and bone marrow cavities. (A) Low magnification, (B) High magnification. Adipose tissue • Adipose tissue is a specialized connective tissue that play a role in storage of fat. • Adipose tissue consists of adipocytes/fat cells. • There are two types of adipose tissue: A. White/yellow adipose tissue B. Brown adipose tissue Yellow adipose tissue Yellow adipose tissue The blood tissue:The blood is an opaque, rather viscous fluid that is bright red when Oxygenated and dark red when depleted of oxygen. - The elements of blood consist of: - 1-erythrocytes(red blood cells):- they are non-nucleated cells with depressed center that contain hemoglobin, they are most numerous elements around 4.5 to 5.5 million cells per cubic millimeter. 2-Leukocytes(white blood cells):- they are of two typesa-granulocytes-they are so named because they have conspicuous granules in there cytoplasm (neutrophils, eosinophils, basophils). - b-A granulocytes-lack pronounced granules in the cytoplasm (monocytes, lymphocytes). 3-bloodplatelets:- they are non-cellular elements in the blood that assist in the blood clotting process. Elements of blood Human blood smear, with RBCs, WBCs and platelets Basophil Eosinophil Thank you