Join Dr. Muhammad Ali Rabbani, Assistant Professor of Anatomy, for an enlightening exploration of advanced concepts in the histology of connective tissue. Building upon foundational knowledge, this lecture delves into the histological features, classification, and functional significance of various types of connective tissue, providing a comprehensive understanding of their roles in maintaining tissue integrity and homeostasis. From the dynamic interplay of cells and extracellular matrix components to the clinical correlations and medical applications, embark on a journey through the intricacies of connective tissue histology with Dr. Rabbani as your guide. 🔬 Key Topics Covered: - Interstitial Fluid: Explore the composition and physiological significance of interstitial fluid in connective tissue, including its role in maintaining tissue hydration, nutrient exchange, and waste removal. - Types of Connective Tissue: Examine the diverse types of connective tissue, including connective tissue proper, embryonic connective tissue, and specialized variants, and understand their structural characteristics, cellular composition, and functional adaptations. - Histological Features: Investigate the histological features of connective tissue, ranging from loose and dense connective tissue to specialized types such as reticular and mucoid connective tissue, and comprehend their unique properties and functions. - Adipose Tissue: Gain insight into the structure, function, and histogenesis of adipose tissue, including the classification of white and brown adipose tissue, their physiological roles, and regulatory mechanisms. - Clinical Correlations: Explore the clinical relevance of connective tissue histology in health and disease, including its implications for tissue repair, inflammation, metabolic disorders, and therapeutic interventions. 🎓 Learning Objectives: By the end of this session, students will: - Describe the composition and functions of interstitial fluid in connective tissue. - Summarize the histological features and classification of various types of connective tissue. - Compare and contrast different types of connective tissue based on cellular composition, fiber arrangement, and functional adaptations. - Explain the physiological roles of adipose tissue and its significance in metabolic regulation, thermogenesis, and pathological conditions. 💡 Medical Applications: - Apply knowledge of connective tissue histology to interpret histopathological findings, diagnose connective tissue disorders, and develop targeted therapeutic strategies. - Explore research opportunities aimed at unraveling the molecular mechanisms underlying connective tissue physiology and pathology, with implications for regenerative medicine and tissue engineering. 🔍 Connect with Dr. Muhammad Ali Rabbani to deepen your understanding of advanced concepts in connective tissue histology and their clinical relevance! 🔍

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Histology of Connective Tissue II
Dr. Muhammad Ali Rabbani
Asst. Professor Anatomy
MBBS (NMC, Multan)
FCPS (Anatomy)
CHPE (Certificate in Health Professional Education)
DHPE (Diploma in Health Professional Education)
MBA (Masters of Business Administration)
MPH (Masters of Public Health)

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Let’s review the previous lecture
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Which of the following connective tissue components is located in the
ECM but not in the ground substance?
a. Collagen bundles
b. Fibronectin
c. GAGs
d. Hyaluronan
e. Proteoglycans
Dr Muhammad Ali Rabbani 3

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Which of the following connective tissue components is located in the
ECM but not in the ground substance?
a. Collagen bundles
b. Fibronectin
c. GAGs
d. Hyaluronan
e. Proteoglycans
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What cells numerous in loose connective tissue are filled with secretory
granules and stain with metachromasia?
a. Macrophages
b. Mast cells
c. Fibrocytes
d. Active fibroblasts
e. Leukocytes
Dr Muhammad Ali Rabbani 5

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What cells numerous in loose connective tissue are filled with secretory
granules and stain with metachromasia?
a. Macrophages
b. Mast cells
c. Fibrocytes
d. Active fibroblasts
e. Leukocytes
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Which one of the following cell types arises from monocytes?
a. Plasma cells
b. Fibroblasts
c. Lymphocytes
d. Macrophages
e. Mast cells
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Which one of the following cell types arises from monocytes?
a. Plasma cells
b. Fibroblasts
c. Lymphocytes
d. Macrophages
e. Mast cells
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Learning Objectives
By the end of this session students should be able to
• Describe Interstitial Fluid
• Summarize a brief account of histological features of different types
of connective tissue
• Compare various types of connective tissue with example of each
type
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Interstitial Fluid
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Water in the ground substance of connective tissue is referred to as
interstitial fluid
• It has an ion composition similar to that of blood plasma
• It contains plasma proteins of low molecular weight
• As much as one-third of the body’s plasma proteins are normally
found in the interstitial fluid of connective tissue
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• Interstitial fluid is maintained by exchange through capillaries
• Two main forces act on water in capillaries
• Hydrostatic Pressure – forces water out of capillary
• Osmotic Pressure – draws water back into capillaries
• The quantity of water drawn back into capillaries is often less than
what is forced out
• Excess water is drained through the lymphatic vessels
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Types of Connective Tissue
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Different combinations and densities of the cells, fibers, and other ECM
components form different types of connective tissue
Connective Tissues may be broadly classified as follows
• Connective Tissue Proper
• Loose (areolar) connective tissue
• Dense irregular connective tissue
• Dense regular connective tissue
• Embryonic Connective Tissue
• Mesenchyme
• Mucoid (mucous) connective tissue
• Specialized Connective Tissue
• Reticular, Adipose, Cartilage, Bone, Blood connective tissue
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Connective Tissue Proper
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Loose Connective Tissue
• It contains almost equal parts of
• Cells – mostly fibroblasts, other cells also found
• Fibers – Collagen predominate, reticular and elastic tissue also present
• Ground substance
• It has delicate consistency – flexible and not resistant to stress
• Form a layer beneath the epithelial lining of many organs (lamina
propria) and fills the spaces between fibers of muscle and nerve
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Dense Connective Tissue
• It has similar components as loose connective tissue
• ↓ cells – mostly fibroblasts
• ↑ fibres – predominance of bundled type I collagen fibers
• ↓↓ground substance
• Less flexible, more resilient to stress
• It is further divided into two types depending upon orientation of
fibers
• Dense irregular connective tissue
• Dense regular connective tissue
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Dense Irregular Connective Tissue
• Bundles of collagen fibers appear randomly interwoven, with no
definite orientation
• This structure provides resistance to stress from all directions
• Examples include
• Deep dermis layer of skin
• Capsule surrounding most organs
• Submucosa of digestive track
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Dense Regular Connective Tissue
• Consists mostly of type I collagen bundles and fibroblasts aligned in
parallel
• Provide great resistance to prolonged or repeated stresses from the same
direction
• Examples include
• Tendons
• Aponeuroses – collagen exist as multiple layers alternating at 90° angles
• Ligaments – some contain parallel bundles of elastic tissue besides collagen
• Corneal Stroma
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Notice the shape of the Fibroblast

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Reticular Connective Tissue
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• Characterised by abundant fibers of type III collagen (reticulin) forming a delicate
network
• Produced by modified fibroblasts often called reticular cells
• It provides a framework with specialized microenvironments for cells in
hemopoietic tissue and some lymphoid organs ( bone marrow, lymph node,
spleen)
• The resulting cell-lined system creates a meshwork for passage of leukocytes and
lymph
• Examples include
• Bone marrow
• Liver, pancreas
• Adrenal Glands
• All lymphoid organs except thymus
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Mucoid Connective Tissue
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• It consists of
• Abundant ground substance - composed chiefly of hyaluronans
• Sparse collagen fibers
• Scattered fibroblasts cells
• It is a principal component of the fetal umbilical cord, where it is
referred to as Wharton’s jelly
• Similar tissue is found in vitreous chambers of eyes and pulp cavities
of young teeth
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Dense regular connective tissue typically involves which of the
following features?
a. Contains mostly synthetically active fibroblasts
b. Contains much ground substance
c. Contains a similar cell population as areolar connective tissue
d. Predominant tissue type in the stroma of most organs
e. Predominantly located in tendons and ligaments
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Dense regular connective tissue typically involves which of the
following features?
a. Contains mostly synthetically active fibroblasts
b. Contains much ground substance
c. Contains a similar cell population as areolar connective tissue
d. Predominant tissue type in the stroma of most organs
e. Predominantly located in tendons and ligaments
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Adipose Tissue
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Adipocytes
• Fat storing cell of the body
• Location
• Isolated cells
• Small groups in irregular connective tissue
• Large aggregates – Adipose tissue
• 15-20% of Adult body weight
• Rich blood supply and thin external lamina
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Adipocytes
• Functions
• Energy storage
• As endocrine organ
• Insulation
• Space filling
• Shaping of body surface
• Types
• White adipose tissue
• Brown adipose tissue
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White Adipose Tissue
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White Adipose Tissue
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• Cell shape
• Size (50-150µm)
• Appearance (Light microscopic)
• Signet-ring appearance
• Unilocular
• Vimentin in lipid-cytoplasm interface
• Nucleus and Cytoplasm
• Submembranous layer
• SER Cisterns & pinocytic vesicles
• Surrounding reticular fibers

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White Adipose Tissue
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• Distribution
• Age
• Sex
• Colour
• Diet – Carotenoids
• Sources of stored lipids
• Chylomicrons - dietary
• VLDLs - livers
• Synthesised in adipocytes

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Chylomicrons & VLDL
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Lipid Storage and Mobilization
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Role of Insulin
Norepinephrine
Growth hormone
Role of Leptin
Starvation
Release of
Proinflammatory cytokines

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Histogenesis
• Begin to accumulate by 14 weeks
• Proliferation stops by late gestation
• Filling of existing by age of 10
• Period of fat cell differentiation through
adolescence
• Obesity
• Adult - hypertrophy
• Childhood - hyperplasia
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Brown Adipose Tissue
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Brown Adipose Tissue
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• 2-5% of new-born weight
• Reduces greatly with age
• Location
• Back, neck, shoulder
• Adults – kidney, supra-renal, aorta, mediastinum
• Structure
• Smaller
• Colour – blood vessels, mitochondria
• Multilocular
• Function – Heat production
• uncoupling protein-1 (UCP1) or thermogenin

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Brown Adipose Tissue
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Activated hormone sensitive lipase → fatty
acid → not released, rather metabolised →
uncoupling → heat released

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Differences – White vs Brown Adipose Tissue
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• Shape
• Size
• Droplets
• Nucleus location
• Location
• Connective tissue lobules
• Regulation / Innervation
• Origin (location, time)

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Thank You
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