Connective Tissues

❖ Connective Tissues • Connective tissues are fibrous tissues, they are made up of cells separated by extracellular matrix (non-living material). ▪ The extracellular is larger than the cellular material. • All connective tissue except cartilage are vascularized which is contain blood vessels, nerves & lymph vessels. • All connective tissue except blood and lymph consists of three main components: ▪ Fibers such as elastic and collagenous fibers, ground substance and cells. • But blood and lymph lack the fiber components. • The cells of connective tissue include fibroblasts, adipocytes , mast cells , macrophages and leukocytes. • Function : supports, connects, or separates different types of tissues and organs in the body • Connective tissue is found in between other tissues everywhere in the body, including the central nervous system: the meninges membrane cover the brain and the pia matter covers the spinal cord. How are connective tissues broadly subdivided? 1. Connective tissue proper i. Loose (Areolar) connective tissue ii. Dense connective tissue 2. Special connective tissue i. Reticular connective tissue ii. Adipose tissue iii. Cartilage iv. Bones v. Blood ➢ Connective tissue proper 1. Loose (Areolar) connective tissue: • Most common type of connective tissue in vertebrates • Strong enough to bind different tissues together • Soft enough to provide flexibility and cushioning • Function: holds organs in place and attaches epithelial tissue to underlying tissue 1|Page • Location: surrounds blood vessels and nerves • The matrix of this tissue contains many different cells such as : ▪ ▪ ▪ ▪ ▪ ▪ microphage with its nucleus Plasma cells Adipocyte ( fat cell) , the yellow droplets & there is a nucleus in the dark spot mast cell macrophages with its nucleus lymphocytes with its nucleus ▪ The matrix contains three main types of connective tissue fiber, these are: a) Collagenous fibers , thicker than the other fibers. b) Elastic fibers c) Reticular fibers 2. Dense connective tissue: • Extracellular matrix of it composed of collagen fibers • Cell types: fibroblast cells arrange in rows between collagen fibers , this type of cells are fiber forming cells which is mean synthesis the fibers • Dense connective tissue forms strong, rope-like structures (such as tendons and ligaments} or arranged in sheets ( as in the lower layers of the skin (dermis) • There are two types of dense connective tissue: ▪ Dense irregular connective tissue • • • 2|Page Irregular patterns/network of collagen bundles and matrix and sometimes found in the form of a network Collagen fibers ➔ collagen fiber bundle are predominant in this tissue and arrange in irregular butter Contain small amount of elastin fiber ( thinnest fiber) This picture shows you how the fibers arrange , there is irregular arrangement for the collagen fiber ▪ Dense regular connective tissue • • 3|Page Collagen fibers are bundled in a parallel fashion Elastic and reticular fibers are completely absent ➢ Special connective tissue ➢ Reticular connective tissue: ▪ Has a network of reticular fibers that made up of collagen ▪ Reticular fibers are synthesized by special fibroblasts called reticular cells ▪ Reticular fibers are thin branching structures ▪ Function: support the lymphoid organs (lymph node stromal cells, red bone marrow, spleen) and hold adipose tissue in place by form the soft skeleton (stroma) ▪ Extracellular matrix: thinly branched reticular fibers made of collagen ➢ Adipose tissue or fat body : • Composed mostly of adipocytes, fibroblasts, vascular endothelial cells and adipose tissue macrophages • Two types of adipose tissues : ➔ White adipose tissue (WAT), which stores energy ➔ Brown adipose tissue, which generates body heat • Functions: 4|Page 1) 2) 3) 4) Store energy in the form of lipids Cushions Insulation of the body Production hormones such as leptin • Location in humans, adipose tissue is located : 1) Beneath the skin (subcutaneous fat) 2) Around internal organs (visceral fat) 3) In bone marrow (yellow bone marrow) 4) Intermuscular (Muscular system) 5) In the breast tissue • Note : ▪ the vacuole of the fat cell filled with the fat droplet ▪ the nucleus push aside to from a signet like structure ➢ Cartilage : • This cartilage is flexible connective tissue • Cell types: chondrocytes that produce a large amount of collagenous extracellular matrix • Chondrocytes found in a cavity called lacuna • Single cell called chondrocyte , group of cells called condrocyte set • Extracellular matrix: collagenous extracellular matrix containing ground substance that is rich in proteoglycan and elastin fibers 5|Page • Cartilage is avascular and aneural • Nutrients are supplied to chondrocytes via diffusion, so it is rigid • Function: holds tubes open in an animal’s body due to its rigidity • Location: in joints between bones, ribcage, ear, nose, bronchial tubes, intervertebral discs • There are three types that differ in relative amounts of cartilage: 1) Hyaline cartilage , found in the outermost layer of the trachea & its made up from homogeneous matrix , lacuna (inside it there is chondrocytes) 2) Elastic cartilage , is made up from lacuna and chondrocyte or chondrocyte set , the matrix of elastic cartilage its not homogeneous because its imbrinated with the elastic fibers 3) Fibrocartilage , its look like the elastic cartilage but instead of elastic fibers there is collagen fibers , sometimes the cartilage classified which means there is a deposition of calcium in it ➢ Bones : • • Location: skeleton Cell types: osteocytes (living cells embedded in a mineralized organic matrix) found in cavity called lacuna • Extracellular matrix: consists of organic components & inorganic composition , inorganic composition of bone mineral is primarily formed from salts of calcium and phosphate • Function: support and protection • There are two types of bone: cortical bone and cancellous bone ➔ Cortical bone • Consists of a repeating structure called an osteon (Haversian system) 6|Page • Osteons are the primary anatomical and functional unit • Each osteon consists of concentric lamellae (layers) of mineralized matrix • Lamellae are deposited around a central canal, known as the Haversian canal • This canal contains blood and nerve • In the lamellae there are cavities where the bone cell (osteocyte) found around the lacunae • Non-haversian system between the haversian systems ➢ Blood : • Function: delivers nutrients and oxygen to the cells and transports metabolic waste products away from cells • Composition: in human composed of blood cells suspended in blood plasma (Extracellular matrix) 7|Page • Blood plasma makes up 55% of blood, and it is 92% water by volume • Location: blood vessels • The blood cells are mainly : 1) Red blood cells (RBCs or erythrocytes) 2) Thrombocytes (platelets) 3) White blood cells (also called WBCs or leukocytes) • The white blood cells can be classified into: ▪ Agranulocytes (Monocyte and Lymphocyte) ▪ Granulocytes (Eosinophil, Basophil, and Neutrophil) ❖ Muscle tissue • Function: produce force and motion such as movement 8|Page • Location: anchored by tendons to bone (skeletal muscle); walls of organs and internal structures such as intestine (smooth muscle); heart (cardiac muscle) • Soft tissue • There are three types of muscle tissue in mammals: ➢ Skeletal muscle • Function: to effect skeletal movement such as locomotion and to maintain posture • Location: anchored by tendons to bones • Striated • Un branched • Under voluntary control • Muscle fibers are cylindrical more than one nucleus (multi nuclei & multiple mitochondria) • its fibers composed from myofibrils , myofibrils composed of actin & myosin which repeated in units called sarcomeres that’s why its striated • Males: 42% of body weight • Females: 36% of body weight 9|Page ➢ Smooth muscle • Cell of smooth muscle is spindle in shape , uni-nucleated this means each cell contains one nucleus • Function: to facilitate body functions • Location: walls of organs and structures like the esophagus, stomach, intestines, bronchi, urethra, uterus, vaginal wall, bladder, blood vessels, and arrector pili of skin • Contraction of this muscle allow the liquid to pass through these organs • Not striated • Branched • Not under voluntary control by signals from autonomous nervous system as hormones and other chemicals released by organs • Activated by: interaction of CNS • This muscle made up of actin and myosin filaments , but these filament arranged in stacked pattern across the cells that’s why this muscle is not striated 10 | P a g e ➢ Cardiac muscle (myocardium) • It forms the bulk of the heart , its composed from individual heart muscle cell • Cardiomyocytes joined together by intercalated disc • Function: pump blood • Location: heart • Striated like skeletal muscle , due to the structure of the cardiac muscle similar to that of the skeletal muscle • Not under voluntary control uni-nucleated • Branched 11 | P a g e ❖ What does striated mean? ▪ Contains sarcomeres , as we said before muscle fibers composed from myofibrils , myofibrils composed fo actin & myosin filaments , which repeated in units called sarcomeres ❖ What is the difference in orientation between skeletal and cardiac muscle? ▪ Skeletal muscles are arranged in regular, parallel bundles ▪ Cardiac muscles connect at branching, irregular angles called intercalating discs ❖ What is the difference between striated and non-striated muscles? ▪ Striated muscles contract and relax in short, intense bursts ▪ Non-striated muscles sustain longer or even near-permanent contractions 12 | P a g e ❖ Nervous tissue • Function: sensory input, integration, control of muscles and glands, homeostasis, mental activity • Location: main component of the brain and spinal cord (CNS) and the nerves (PNS) • Composed of neurons (nerve cells) and neuroglia (glial cells) • Neurons: receive and transmit impulses • Neuroglia : assist the propagation of the nerve impulse and provide nutrients to the neuron • There are four types of nervous tissue: • Gray matter ▪ Found in CNS ▪ Composed of cell bodies, dendrites, unmyelinated axons, protoplasmic astrocytes, microglia, and very few myelinated axons • White matter ▪ Found in CNS ▪ Composed of myelinated axons, fibrous astrocytes, myelinating oligodendrocytes, and microglia • Nerves ▪ Found in PNS • Ganglia ▪ Found in PNS 13 | P a g e