6th-Connective tissue.pdf

Fakeeh College for Medical Sciences Second year, semester 1, 2023-2024 Medicine Program Connective Tissue Prof. Fatma Ghoneim Professor of Histology & Cell Biology ...

Fakeeh College for Medical Sciences Second year, semester 1, 2023-2024 Medicine Program Connective Tissue Prof. Fatma Ghoneim Professor of Histology & Cell Biology  Learning Objectives By the end of the lecture, you should be able to: 1) Define connective tissue. 2) List cells and fibers of connective tissue. 3) Write the function & structure of each cell. 4) Compare between the different connective tissue fibers. 5) Describe the sites and structure of the different connective tissue types.  Contents 1) Characters & functions of connective tissue. 2) Types & characters of connective tissue fibers. 3) Types & characters of connective tissue cells. 4) Types of connective tissue proper. ❑ Characters of C.T: – Connective tissue cells are widely separated from each other. – It is penetrated by blood vessels, lymphatic and nerves. – It consists of : cells fibers intercellular matrix ❑ Functions of C.T 1. Supports cells, tissues and organs. 2. Medium for exchange of nutrients between the blood and tissues. 3. Protects against microorganisms. 4. Repairs injured tissues. ❑Types of Connective tissue Embryonic connective tissue – Mucoid connective tissue. Connective tissue proper (soft matrix): – Loose areolar. – Reticular. – Dense collagenous (regular and irregular). – Elastic. – Adipose (brown or white). Specialized connective tissue: – Cartilage (rubbery matrix) – Bone (solid matrix) – Blood (fluid matrix)  Connective tissue fibers ❖ Characters & Types: - They are formed of proteins that form elongated structures. - Three main types of fibers: o White Collagen fibers: Strong and resist stretch o Yellow Elastic fibers: Stretchable but regain their original length o Reticular fibers: Form a reticulum (network).  White Collagen Yellow Elastic Reticular Sites Table (in the next slide) The wall of arteries, The supportive network trachea, bronchi & of organs e.g. lymph bronchioles node, spleen and liver. Characters Synthesized by: Synthesized by: Synthesized by: ✓ Fibroblast ✓ Fibroblast. ✓ Reticular cells. ✓ Chondroblast in cartilage. ✓ Osteoblast in bone. The most abundant protein in the human body. L/M Wavy, thick and not Straight, thin & Very thin fibers that branched fibers → form branched fibers. branch and wavy bundles. anastomose to form a network. Stains Hx & E: acidophilic Hx & E: acidophilic. Hx & E: not stained Masson trichrome stain: Orcein stain: reddish can be stained by appear blue or green brown silver and PAS Van Gieson stain: yellow  Types & Sites of collagen According to the amino acids sequence, there are many types of collagen fibers Type Site Type I Tendons, ligaments, bones, dermis of the skin, dentin Type II Cartilage Type III Reticular fibers (present in network that supports the organs e.g. liver, spleen and kidney) Type IV The basal lamina (basement membrane). White Collagenous fibers Elastic fibers stained by Elastic fibers stained by orcein stain Hx &E Reticular fibers stained by Silver stain  C.T cells Free Fixed 1- Free macrophages. 1. Stem cells: 2- Plasma cell. UMC Pericytes 3- Mast cells. 2. Fibroblast. 4- Pigment cell. 3. Reticular cells. 5- Leukocytes. 4. Fixed macrophages. 5. Fat (adipose) cells. * Nonstable & short lived *Stable & long lived  1- Undifferentiated mesenchymal cells (UMC) Site: young embryonic mesenchymal tissue. L/M ✓ Shape: Branched. ✓ Cytoplasm: Basophilic. ✓ Nucleus: large, oval, open face. E/M: the usual organelles. Function Can differentiate to other C.T cells.  2- Pericytes Origin: UMC Site: Partially surround the endothelium of blood capillaries L/M, E/M & Function: Similar to UMC.  3- Fibroblasts Origin: UMC, pericytes Site: The most common C.T cell Types: ✓ Active fibroblast ✓ Inactive fibroblast ( fibrocyte) Active fibroblast: L/M: ✓ Shape: Branching with multiple processes. ✓ Cytoplasm: Deep basophilic. ✓ Nucleus: Oval, open face (lightly stained). E/M: Characters of protein secretory cells (ribosomes, RER, Golgi & Mitochondria)  Function Synthesis of collagen fibers. Synthesis of the matrix. Healing and repair of the injured C.T. Fibrocytes L/M: ✓ Shape: Spindle shaped with less processes. ✓ Cytoplasm Pale basophilic. ✓ Nucleus: Flat, dark face (deeply stained) E/M: Fewer organelles Function: Change to active fibroblast in time of need e.g. wound healing  4- Reticular cells Origin: UMC Site: parenchymatous organs: liver, spleen & kidney L/M & EM: Similar to fibroblast. Function: Reticular fibers formation. Q: List the branched connective tissue cells and describe one of them.  5- Macrophages Origin: Blood monocytes Sites and types: ✓ Langerhans cells in skin. ✓ Macrophages of spleen, Lymph nodes. ✓ Microglia in brain. L/M: ✓ Shape: large irregular cell. ✓ Cytoplasm: Pale basophilic ✓ Nucleus: kidney shaped. ✓ Special Stain: Trypan blue E/M: lysosomes, phagocytic vacuoles, the usual organelles Function: Phagocytosis of resistant bacteria and viruses.  6- Fat cells Origin: UMC Types: - Unilocular - Multilocular  Unilocular (white) Multilocular (brown) Site Subcutaneous tissue, around blood Fetuses and newborn vessels and kidney. (Adults have little amount) Shape Large ovoid cells Smaller than unilocular Nucleus Peripheral and flat Central and rounded Cytoplasm L/M: Contains a large single fat L/M: Contains multiple fat droplets droplet, pushing the cytoplasm and nucleus peripherally (signet ring appearance). Special stain: It could be stained by sudan III stain: orange color -E/M: - Large lipid droplets E/M: - Numerous mitochondria - Few cell organelles around the surrounding the fat droplets nucleus. - Few other organelles Function -Synthesis and storage of fat Heat generation -Supporting function e.g. fat around the kidney Unilocular fat cell stained Unilocular fat cell stained by Hx & E by Sudan III Unilocular (white) fat cell Multilocular Unilocular Multilocular (brown) fat cell  7- Plasma cell Origin: Activated B-lymphocytes. L/M: ✓ Shape: oval. ✓ Cytoplasm: deep basophilic with Negative Golgi image. ✓ Nucleus: rounded, eccentric, cartwheel or clock fac appearance (due to special arrangement of chromatin) E/M: Characters of protein secretory cells: (ribosomes, rER, well developed Golgi, mitochondria) Function: Synthesis and secretion of antibodies  8- Mast cell Origin: Stem cells in the bone marrow. L/M: ✓Shape: Oval or rounded cells. ✓Cytoplasm basophilic and contains basophilic granules (like basophils) ✓Nucleus central, rounded, may be masked by the granules. Mast cells granules are metachromatically red stained by toluidine blue E/M: -Organelles (Golgi, rER, mitochondria) -large number of electron dense granules. Function: Synthesis, storage and secretion of: Histamine and heparin  9 – Pigment cells Contain melanin granules and are responsible for eye coloration. 10-Extravasated leucocytes  Intercellular matrix ❑Ground substance: - Biochemically it is glycoproteins and proteoglycan. - It is secreted mainly by fibroblasts ❑Tissue fluid: - Derived from the blood capillaries (soft matrix).  Types of the connective tissue proper 1. Loose areolar. 2. Dense collagenous (regular and irregular). 3. Reticular. 4. Elastic. 5. Adipose (white and brown).  1- Loose (areolar) C.T ✓ It is the most common type of C.T Structure: ✓ Most of C.T cells (pericytes, fibroblasts, macrophages, plasma, reticular cells, leucocytes…… ………) ✓ Collagen, elastic and reticular fibers. Sites: ✓ Surrounds blood vessels and nerves. ✓ Under the epithelial tissue of different organs.  2- Dense collagenous C.T (Regular and Irregular) A- Dense regular collagenous C.T (White fibrous C.T) Structure: ✓ Densely packed parallel bundles of collagen fibers , with fibroblasts and fibrocytes in between. Sites: - Tendons. - Ligaments. B-Dense irregular collagenous C.T Structure: ✓ Irregularly arranged collagen fibers with fibroblasts and fibrocytes in between Sites: - Capsules of the organs e.g. liver and spleen. - Dermis of skin.  3- Reticular C.T Structure: ✓ Reticular cells and fibers that form a network. Sites: ✓ The supportive network of organs e.g. lymph node, spleen and liver. 4- Elastic C.T Structure: - ✓ Elastic fibers that form thick regular parallel bundles with Fibroblasts Sites: ✓ Vocal ligament. ✓ Trachea & bronchi. ✓ Aorta. ✓ Arteries.  5- Adipose C.T ❑ There are two types: White adipose C.T: formed of unilocular fat cells - fat storage. Brown adipose C.T: formed of multilocular fat cells – heat generation. Brown Adipose White Adipose  Mucoid connective tissue Structure: ✓ Undifferentiated mesenchymal cells and fibroblasts with few collagen fibers. Sites: ✓ Umbilical cord ✓ Vitreous humor of the eye.  Basement membrane Definition: It is a sheet like structure located between epithelial tissue and the underlying connective tissue. Structure: ▪ They are formed of protein, glycoproteins , and Type IV collagen. By LM: - It is visible by light microscope and stained by PAS. Function: ▪ It supports and binds the cells to C.T. ▪ It acts as diffusion barrier between C.T and other tissues.  References Junqueira’s Basic histology text & Atlas. McGraw-Hill Education (2018). 15th edition Chapter: 5 Pages: 98: 117  Summary The connective tissue is formed of cells, fibers and ground substance. The cells is divided into 2 categories: free or fixed. The UMC and pericytes are regenerative cells. Fibroblast and reticular cells synthesize the matrix. Macrophage and other leucocytes defense against microorganisms Mast cells are responsible for allergic response against the antigen. Unilocular fat cell store fats and multilocular produce heat for the newborns and infants.  Assignment List the connective tissue cells and describe the histology of one of the branched cells. Compare between white & brown fat cells. Student Activity 1) Which of the following can be classified as "specialized connective tissue"? a. Mesenchyme. b. Mucous connective tissue. c. Dense connective tissue. d. Blood. e. Loose connective tissue. 2) Which of the following can be classified as "embryonic connective tissue"? a. Cartilage. b. Mucoid connective tissue. d. Adipose tissue. d. Bone. e. Blood. 3) Which one of the following is a fixed connective tissue cell? a) Fibroblast. b) Mast cell. c) Plasma cell. d) Pigment cell. e) Neutrophil. 4) Trypan blue stain is used to detect the following cell: a- Plasma cell. b- Reticular cell. c- Macrophage cell. d- Mast cells. e-Fibroblast. 5) Metachromasiais a feature of: a. Mast cell. b. Adipocyte. c. Macrophages d. Mesenchymal cells. e. Reticular cells 6) A 7-year- old male child came to the clinic with his mother who told the doctor that her child complains of itchy skin, cough and dyspnea especially when he eats chocolate or strawberry. She added that her brother was suffering from this allergic condition. Which of the following cells is responsible for this condition? (A) Fibroblasts. (B) Neutrophils. (C) Pericytes. (D) Macrophages. (E) Mast cells.