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Connective Tissue
General Characteristics
- Composed of widely scattered cells that lie within a large amount of nonliving intercellular material. (living cells surrounded by a matrix)
- Cells of connective tissue are of two types:
- One produces and maintains intracellular material
- The other protects the body from infection Connective Tissue Function
- Connects, supports, binds or separate different types of tissue and organs in the body
- Develop from the mesoderm
- Found in b/w other tissue everywhere in the body, including the nervous system Germ Layers Ectoderm:
- The outermost layer, it forms the nervous system (brain and spinal cord), skin, hair, nails, and the lining of the mouth, nose, and anal canal. Mesoderm:
- The middle layer, it develops into muscles, bones, cartilage, blood, blood vessels, the heart, kidneys, and the reproductive system. Endoderm:
- The innermost layer, it forms the lining of the digestive and respiratory systems, including the liver, pancreas, thyroid, and many other internal organs. These layers give rise to all tissues and organs in the body. Key points about the germ layers: Gastrulation:
- The process of forming these layers is called gastrulation and occurs during the early stages of embryonic development. Differentiation:
- Cells from each germ layer differentiate and specialize to form specific tissues and organs Connective Tissue Classifications of Connective Tissue There are four classifications of connective tissue: โ Connective Tissue Proper Cartilage
โ Cartilage โ Bone Blood โช Blood composition: โช 45% cellular, โช 55% non-living matrix (plasma)
- Blood is considered part of connective tissue because it shares a common origin (mesenchyme) and has cells living in a non-living matrix. Connective Tissue Characteristics Connective Tissue: โ Shares a common origin (mesenchyme). โ Has cells living in a non-living matrix.
Matrix: โ Composed of fibers and ground substance.
Fibers: โ Collagen: Thick, pink. โ Elastic: Purple/black. โ Reticular: Fine, black.
Histological Characteristic of Connective tissue
- Cell
- Nucleus
- Fiber
- Ground Substance Cells
- Connective tissue proper - fibroblast
- Cartilage- chondrocytes
- Osteocytes- bone
- Blood - RBC Mixture of Cells Fibroblast - โ Mostt common cells in connective tissue โ Their nuclei are ovoid or spindle shaped and can be large or small in size depending on their stage of cellular activity โ Synthesis ECM and collagen
Macrophages - โ Highly phagocytic cells that are derived from blood monocytes โ With conventional staining, macrophages are very difficult or identify unless they show visible ingested material inside their cytoplasm
Mast Cells โ Bone marrow origin and are distributed chiefly around small blood vessels โ They are oval to round in shape, with a centrally placed nucleus
Plasma Cells โ Derived from B lymphocytes โ They are oval shaped and have the ability to secrete antibodies That are antigen specific
Leukocytes - white blood cells are considered the transient cells of connective tissue. They migrate from the blood vessels into connective tissue by the process of diapedesis โ Neutrophils โ Eosinophils โ Basophils
Adipocytes( fat Cell) Arise from undifferentiated mesenchymal cells of connective tissue
Extra Cellular Matrix
โ Dense refers to the high abundance of collagen fibers ( but fewer cells) compared to loose connective tissue โ Irregular indicates that the orentation of the fiber bundles is many different locations ( or randomly oriented bundles โ Contains mostly collagen fibers with a lesser number of other fibers such as elastic fiber. The skin has a thick layer of dense irregular connective tissue with fibers arranged in various directions to resist stretching forces in any direction
Dense Regular CT โ This type of tissue is composed of coarse collagen bundles that is densley pack and oriented into parallel fibers โ The nuclei of the fibroblast are visible, but the cytoplasm is not easily seen โ The thick bundles of collagen fibers fill the intercellular spaces โ Dense irregular connective tissue provides resistance to traction forces in tendons and ligaments โ Function: provide strong attachment between various structure. Loose CT โ Loose connective tissue is also called areolar connective tissue โ This type of connecctive tissue has abundant ground substance, with any connective tissue cells and relatively few fibers โ It is richly vascularized, flexible , and not highly ressitant to stress โ The lamina propria of the digestive tract is an extree example of a loose Connetcive tissue The tissue lies immediately beneath the thin epithelium of the gut, which is one place where the body's defense mechanisms intially attacks bacteria and pathogens
โ Therefore, plasma cells, Mast cells, leukocytes, and fibroblast are common in this area Loose connective tissue is characterized by loosely arranged, woven connective fibers, abundant ground substance , and tissue fluid, which contains the rich array of connective tissue cells
Loose connective Tissue Areolar Many fibers that support and bind other tissues as well as empty space for storing tissue fluid Must abundant connective tissue Adipose Contains many fat cells which stores nutrients and also serve to insulate the body Recticular Similar to areolar tissue but contains only reticular fibers and support certain structures in the body Dense Regular Many collagen fibers packed together with fibroblast in between which resist tension Irregular Many collagen fibers, not arranged in any pattern which offers resistance in many directions Elastic Similar to dense regular but more elastic
Elastic Similar to dense regular but more elastic Specialized Connective Tissues
- Adipose Tissue
- Reticular Connective Tissue
- Elastic Connective Tissue
- Mucous Connective Tissue Adipose Connective Tissue
- Adipose tissue is a specialized form of connective tissue with a rich neurovascular supply.
- Adipocytes (fat cells) are scattered within a loose collagenous supporting tissue in unilocular adipose tissue. Each adipocyte: โ Contains a single large drop of lipid. โ Has a thin rim of cytoplasm around the lipid. โ Has a flattened nucleus located in the periphery of the cell.
Adipocytes are: โ The primary site for storage of energy. โ Regulated by hormonal factors (steroids, insulin, thyroid hormone, etc.) for lipid deposition and mobilization. โ Involved in the synthesis of some hormones such as leptin.
- Adipocyte numbers may increase during childhood depending on nutrition and other factors, but normally remain constant in adulthood. Reticular Connective Tissue
- Reticular tissue is a specialized loose connective tissue. Provides a delicate supporting framework for many highly cellular organs, such as: โ Endocrine glands โ Lymphoid organs โ Spleen โ Liver
- Arranged in a net-like framework to support parenchymal cells (e.g., pancreatic cells).
- Reticular fibers consist of collagen type III, forming a mesh-like network that supports liver cells and holds these cells together.
- Sinusoids run between the reticular fibers. Elastic Connective Tissue
- Elastic connective tissue consists predominantly of elastic material, allowing distension and recoil of the structure. Found in: โ Vertebral ligaments โ Arterial walls โ Bronchial tree
Thick bundles of elastic lamellae are arranged in parallel wavy sheets, with smooth muscle cells and collagen fibers insinuated between alternating lamellae.
- Elastic fibers are formed by elastin and fibrillin micro-fibrils.
- Elastic connective tissue is able to recoil after stretching.
- This property in large arteries helps to moderate the extremes of pressure associated with the cardiac cycle.
- Abnormal expression of the fibrillin (FBN1) gene is associated with abnormal elastic tissue disease. Mucous Connective Tissue
- Found in the lumen of the umbilical vein. Components: โ Fibroblasts โ Collagen fibers Mucous ground substance
Characteristics of Cartilage Types Hyaline Cartilage โ No visible fibers โ Glassy and smooth
Elastic Cartilage โ Elastic fibers in between tightly packed lacunae
Fibrocartilage โ Edges appear as hyaline cartilage (if visible) โ Scattered lacunae โ Wavy collagen fibers
Cartilage General Information Function โ Strong yet flexible โ Absorb shock โ Avascular
Cartilage Types and Locations Hyaline cartilage โ Ribs โ Articular cartilage (synovial joints)
Elastic cartilage โ Ear
Fibrocartilage โ Intervertebral discs (IV discs) โ Pubic symphysis โ Meniscus
Cartilage Cells
- Chondroblasts: Maintain cartilage
Part A: Multiple Choice (1 point each) Which of the following is NOT a function of connective tissue? โ a) Transportation of gases โ b) Structural support โ c) Absorption of nutrients โ d) Immunological defense
Which fiber type provides tensile strength to connective tissue? โ a) Reticular โ b) Collagen โ c) Elastic โ d) Microtubules
Type IV collagen is primarily found in: โ a) Articular cartilage โ b) Basement membranes โ c) Tendons โ d) Loose connective tissue
Which connective tissue cell type is directly responsible for antibody production? โ a) Mast cells โ b) Fibroblasts โ c) Plasma cells โ d) Macrophages
Reticular fibers are composed of which type of collagen? a) Type I
Part A: Multiple Choice (1 point each)
Choose the best answer. What is the embryonic origin of all connective tissue? a) Ectoderm b) Endoderm c) Mesoderm d) Epidermis
Which cell synthesizes extracellular matrix and collagen in connective tissue? a) Mast cell b) Plasma cell c) Fibroblast d) Macrophage
Which of the following is NOT a component of the extracellular matrix? a) Ground substance b) Fibers c) Blood plasma d) Water
Which collagen type is found in basement membranes? a) Type I b) Type III c) Type IV d) Type V
Which connective tissue fiber allows tissues to return to original shape after stretching? a) Collagen b) Reticular c) Elastic d) Fibrillin
The lamina propria of the gut is primarily composed of: a) Dense irregular CT b) Loose (areolar) CT c) Reticular CT d) Cartilage
Which cell type secretes antigen-specific antibodies? a) Neutrophil b) Plasma cell c) Mast cell d) Eosinophil
Reticular fibers are made of: a) Type I collagen b) Type III collagen c) Elastin d) Fibrin
What gives cartilage its flexibility and strength without blood vessels? a) Dense fibers b) Ground substance c) Chondrocytes d) Matrix
Which specialized connective tissue contains reticular fibers and sinusoids? a) Elastic b) Dense regular c) Reticular d) Adipose
Part B: True or False (1 point each)
- ___ Cartilage is highly vascularized.
- ___ Collagen fibers resist tensile forces.
- ___ Ground substance is mostly solid and dense.
- ___ Mast cells arise from bone marrow.
- ___ Fibroblasts are the most common cells in connective tissue.
- ___ Reticular tissue supports organs like the spleen and liver.
- ___ Plasma cells are derived from T-lymphocytes.
- ___ Plasma cells are derived from T-lymphocytes.
- ___ Dense regular connective tissue has collagen fibers in random directions.
- ___ Adipocytes are involved in hormone synthesis.
- ___ Elastic fibers are composed of elastin and fibrillin.
Part C: Fill in the Blank (1 point each)
- ____________ is the process by which white blood cells exit blood vessels into tissue.
- The three germ layers formed during gastrulation are ectoderm, mesoderm, and ____________.
- ____________ connective tissue is found in tendons and ligaments.
- ____________ connective tissue is found in the umbilical cord.
- Glycosaminoglycans are found in the ____________ of connective tissue.
Part D: Short Answer (2 points each)
- Describe the structural difference between dense regular and dense irregular connective tissue.
- What are the roles of fibroblasts and mast cells in connective tissue?
- How does the extracellular matrix contribute to connective tissue function?
- Name and briefly describe the three types of cartilage and their locations.
- Explain how adipose tissue functions in energy storage and hormone regulation.
Part E: Matching (1 point each)
Match each term with the correct description: Term Description A. Type I Collagen ___ 31. Found in skin, bone, and tendons B. Elastic Fibers ___ 32. Allow recoil and stretch C. Mucous CT ___ 33. Found in the umbilical cord D. Macrophage ___ 34. Derived from blood monocytes E. Ground Substance ___ 35. Gel-like material with GAGs
