Cell Adhesion and Junctions

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Questions and Answers

What is the primary function of desmosomes?

To provide points of strong intermediate filament adhesion between adjacent cells (correct)

To connect the cell with the basement membrane

To form gap junctions between cells

To form structural links between actin cytoskeleton and FCM proteins

Which type of cell junction is responsible for attachment of actin filaments into the basal lamina?

Gap junctions

Focal adhesions (correct)

Hemidesmosomes

Desmosomes

What is the primary function of gap junctions?

To form structural links between actin cytoskeleton and FCM proteins

To connect the cell with the basement membrane

To provide points of strong intermediate filament adhesion between adjacent cells

To connect two cells and permit the exchange of ions, metabolites, and electrical signals (correct)

What is the characteristic of microvilli?

Specialized for absorption Signup and view all the answers

What is the primary function of stereocilia?

To enable the detection of light, odors, motion, and flow of liquids Signup and view all the answers

What is the characteristic of cilia?

Motile Signup and view all the answers

What is the function of primary cilia?

To detect light, odors, motion, and flow of liquids Signup and view all the answers

What is the function of Polycystin 1 and 2?

To form channels that open in response to deflection Signup and view all the answers

What is the main function of dynein in cilia and flagella?

To catalyze ATP hydrolysis for microtubule movement Signup and view all the answers

Which of the following is NOT a characteristic of cadherins?

They are involved in cell signaling pathways Signup and view all the answers

What is the primary function of selectins?

To bind to specific oligosaccharide groups Signup and view all the answers

What is the name of the syndrome caused by immotile cilia due to mutations in dynein arms?

Kartagener syndrome Signup and view all the answers

What is the name of the protein complex that establishes weak intercellular connections?

Nectin complex Signup and view all the answers

Which of the following is an example of a Ca+2 independent cellular adhesion molecule?

ICAM Signup and view all the answers

What is the name of the disease caused by autoimmune reactions against desmoglein?

Pemphigus vulgaris Signup and view all the answers

Which of the following is a function of integrins?

To enable cell aggregation and migration Signup and view all the answers

What type of fibers are present in the tunica adventitia?

Elastic and collagen Signup and view all the answers

What is the function of the lymphatic vessels?

To remove excess fluid accumulated in interstitial spaces Signup and view all the answers

What type of connective tissue is present in the visceral layer of the pericardium?

Areolar tissue Signup and view all the answers

What is the function of the valves in the heart?

To prevent backflow of blood Signup and view all the answers

What is the pathway of the impulse-conducting system in the heart?

SA node → AV node → Purkinje fibers Signup and view all the answers

What type of muscle cells are present in the myocardium?

Cardiac muscle cells Signup and view all the answers

What is the function of the fibrous network in the heart?

To serve as an attachment site for cardiac muscle and valves Signup and view all the answers

What is a characteristic of the lymphatic vessels?

They are not found in cartilage or bone Signup and view all the answers

What is the primary function of osteoclasts?

To resorb organic and inorganic matrix components Signup and view all the answers

What is the purpose of the acidic environment created by osteoclasts?

To decalcify the bone's surface Signup and view all the answers

Which hormone inhibits bone reabsorption?

Calcitonin Signup and view all the answers

What is the role of gap junctions in osteocytes?

To allow for communication between osteocytes Signup and view all the answers

What is the function of osteoprotegerin (OPG) produced by osteoblasts?

To inhibit differentiation of osteoclasts Signup and view all the answers

What is the site of secretion of acids and hydrolases in osteoclasts?

Ruffled border Signup and view all the answers

Which of the following hormones does not have receptors on osteoclasts?

Parathyroid hormone (PTH) Signup and view all the answers

What is the role of osteocalcin produced by osteocytes?

To promote bone formation Signup and view all the answers

What is the function of eosinophilic cationic protein in relation to parasites?

It causes the fragmentation of parasites with MBP Signup and view all the answers

What is the primary function of basophils in the immune system?

To mediate hypersensitivity and anaphylactic reactions Signup and view all the answers

What is the function of histamine released by basophils?

To increase the permeability of blood vessels Signup and view all the answers

Which type of granule is found in basophils?

Specific granules Signup and view all the answers

What is the function of monocytes in the immune system?

To phagocytose foreign particles and produce cytokines Signup and view all the answers

What is the function of alpha granules in platelets?

To contain PF4, fibrinogen, and plasminogen Signup and view all the answers

What is the primary function of lymph nodes in the immune system?

To activate T-cells and B-cells Signup and view all the answers

Which type of immune cell is involved in the phagocytosis of foreign particles?

Monocytes Signup and view all the answers

What is the characteristic of apocrine glands?

They secrete by apical portion of cytoplasm into a duct. Signup and view all the answers

What is the function of tight junctions?

To prevent free passage of substances between lumen of natural tract and basolateral intercellular space. Signup and view all the answers

What is the type of gland that is classified as a simple tubular branched gland?

Glands of stomach and uterus Signup and view all the answers

What is the function of laminin in basement membranes?

To facilitate cell adhesion and signal transduction. Signup and view all the answers

What is the characteristic of holocrine glands?

They secrete by shedding entire cells from the lining of the duct. Signup and view all the answers

What is the type of protein involved in tight junctions?

Occludins and Claudins Signup and view all the answers

What is the type of gland that is classified as a compound tubular gland?

Glands of oral cavity Signup and view all the answers

What is a characteristic of tunica media in muscular arteries?

Composed of multiple layers of fenestrated elastic lamellae Signup and view all the answers

What is the component of basement membranes that is responsible for cell adhesion and signal transduction?

Laminin Signup and view all the answers

Which of the following compounds undergoes transcytosis in ECs?

All of the above Signup and view all the answers

What is unique about the structure of elastic arteries?

Alternating layers of fenestrated elastic lamellae and smooth muscle fibers in tunica media Signup and view all the answers

What is the main difference between muscular arteries and arterioles?

Absence of elastic laminae in arterioles Signup and view all the answers

Which type of vessel is typically found branching to form networks of capillaries?

Arterioles Signup and view all the answers

What is the function of eosinophilic cationic protein in relation to parasites?

Fragmentation of parasites with MBP Signup and view all the answers

What is a characteristic of venules?

Presence of pericytes Signup and view all the answers

What is the primary function of basophils in the immune system?

Release of histamine during allergic reactions Signup and view all the answers

Which type of vessel has a thicker tunica adventitia compared to the media?

Elastic arteries Signup and view all the answers

What type of granules are found in basophils?

Specific granules Signup and view all the answers

What is unique about the structure of elastic arteries compared to muscular arteries?

Presence of more elastic material in tunica media Signup and view all the answers

What is the function of monocytes in the immune system?

Phagocytosis of foreign particles Signup and view all the answers

What is the function of alpha granules in platelets?

Storing Pf4, Fibrinogen, and Plasminogen Signup and view all the answers

What is the primary function of lymph nodes in the immune system?

Filtering of lymph to trap pathogens Signup and view all the answers

What is the function of histamine released by basophils?

Inflammation and allergic reactions Signup and view all the answers

Which type of immune cell is involved in the phagocytosis of foreign particles?

Monocytes Signup and view all the answers

What is the primary function of blood in the body?

To transport oxygen and nutrients to cells Signup and view all the answers

What is the composition of plasma in blood?

Water 92%, proteins 7%, other 1% Signup and view all the answers

What is anemia characterized by?

Concentration of erythrocytes or Hb below normal range Signup and view all the answers

What is the function of neutrophils in the immune system?

To destroy invading microorganisms by phagocytosis and secreting proteases Signup and view all the answers

What is the name of the disease caused by a point mutation in hemoglobin?

Sickle Cell Anemia Signup and view all the answers

What is the primary function of erythrocytes in the body?

To transport oxygen from lungs to tissues Signup and view all the answers

What is the composition of the buffy coat in blood?

Platelets and leukocytes Signup and view all the answers

What is the characteristic of erythrocytes?

They are anucleated and practically contain no organelles Signup and view all the answers

What is the thickest layer of the heart wall?

Tunica adventitia Signup and view all the answers

What type of fibers are present in the tunica adventitia?

Collagen and elastic fibers Signup and view all the answers

What is the function of the valves in the heart?

To prevent backflow of blood Signup and view all the answers

What is the pathway of the impulse-conducting system in the heart?

Sinoatrial node → atrioventricular node → Purkinje fibers Signup and view all the answers

What type of muscle cells are present in the myocardium?

Cardiac muscle cells Signup and view all the answers

What is the function of the lymphatic vessels?

To remove excess fluid from interstitial spaces Signup and view all the answers

What is the characteristic of the flow of lymph?

Low pressure and unidirectional Signup and view all the answers

What is the function of the fibrous network in the heart?

To serve as an attachment site for cardiac muscle and valves Signup and view all the answers

What type of joint has a thick pad of fibrocartilage?

Symphysis Signup and view all the answers

What is the function of chondrocytes in cartilage?

To provide structural support to the cartilage Signup and view all the answers

What is the type of collagen found in hyaline cartilage?

Type II collagen Signup and view all the answers

What is the function of the anulus fibrosus in intervertebral discs?

To absorb shock Signup and view all the answers

What is the genetic defect that leads to achondroplasia?

Mutation in FGFR3 Signup and view all the answers

What is the type of connective tissue that is avascular and has a firmer ECM than loose connective tissue?

Cartilage Signup and view all the answers

What is the function of type A synovial cells in the joint capsule?

To remove debris and foreign particles Signup and view all the answers

What is the type of cartilage that has elastic fibers in its matrix?

Elastic cartilage Signup and view all the answers

What is a characteristic of active fibroblasts?

Many cell projections Signup and view all the answers

What is the function of fibronectin in ECM?

Mediates cell adhesion to ECM by binding to integrins on cell surface Signup and view all the answers

What is the function of entactin/nidogen in ECM?

Binds laminin with collagen type IV in lamina densa Signup and view all the answers

What is the function of tenascin in ECM?

Secreted by glial cells in developing nervous system Signup and view all the answers

What is the function of macrophages in the immune system?

All of the above Signup and view all the answers

What is the difference between M1 and M2 macrophages?

M1 promotes inflammation while M2 promotes rebuilding of ECM Signup and view all the answers

What is the characteristic of histiocytes?

Found in connective tissue proper Signup and view all the answers

What is the function of laminin in ECM?

Binds to integrins, heparan sulfate, type IV collagen, and entactin Signup and view all the answers

What is the main difference between hyaline cartilage and elastic cartilage?

The presence of elastic fibers Signup and view all the answers

What is the function of the axon hillock in a neuron?

To integrate synaptic inputs and generate action potentials Signup and view all the answers

What is the characteristic of fibrocartilage?

It lacks a perichondrium Signup and view all the answers

What is the function of the inner cellular layer of the perichondrium?

To contain chondrogenic cells Signup and view all the answers

What is the main component of the hypolemmal cisternae in neurons?

Ca+2 and proteins Signup and view all the answers

What is the characteristic of neurons?

They are postmitotic cells Signup and view all the answers

What is the function of the perikaryon in a neuron?

To contain organelles and nucleus Signup and view all the answers

What is the type of collagen found in the outer fibrous layer of the perichondrium?

Type I collagen Signup and view all the answers

What is the main function of desmosomes in relation to cells?

To provide Mechanical strength to cells Signup and view all the answers

What is the primary component of the ground substance in ECM?

Glycosaminoglycans Signup and view all the answers

What is the function of fibronectin in ECM?

To bind to receptors on the cell surface Signup and view all the answers

What is the main function of loose connective tissue?

To store water Signup and view all the answers

Which type of GAG is the most ubiquitous?

Hyaluronan Signup and view all the answers

What is the function of proteoglycans in ECM?

To bind to other components of ECM and to receptors on the cell surface Signup and view all the answers

What is the main function of adipose tissue?

To store fat Signup and view all the answers

What is the function of perlecan in ECM?

To form part of the basal lamina Signup and view all the answers

What is the primary function of myeloperoxidase in neutrophils?

To act as a marker enzyme for neutrophils Signup and view all the answers

Which type of granule in neutrophils contains lactoferrin?

Specific granules Signup and view all the answers

What is the purpose of the acidification of phagosomes in neutrophils?

To create an environment for enzyme activity Signup and view all the answers

What is the function of eosinophil peroxidase?

To bind to microorganisms and facilitate their killing by macrophages Signup and view all the answers

Which compartment of neutrophils is responsible for the storage of granules?

Storage compartment Signup and view all the answers

What is the function of cathelicidin in neutrophils?

To function similar to antibodies Signup and view all the answers

What is the role of defensins in neutrophils?

To function similar to antibodies Signup and view all the answers

Which type of granule in neutrophils contains lysozyme?

Specific granules Signup and view all the answers

Study Notes

Cell Adhesion and Junctions

Desmosomes: provide strong intermediate filaments between adjacent cells, strengthening tissue, and contain cadherins.
Hemidesmosomes: connect cells to basement membrane, anchoring intermediate filaments of the cytoskeleton into the basement membrane, commonly found in epidermis, vagina, cervix, and cardiac muscle tissue.
Focal adhesions: form a structural link between the actin cytoskeleton and focal adhesion molecules (integrins, talin, vinculin, and focal adhesion kinase), responsible for attaching actin filaments to the basal lamina.
Gap junctions: formed by connexons, connect two cells, allowing for electronic and metabolic coupling, found in epithelia, cardiac muscle, hepatocytes, osteocytes, odontoblasts, and granulosa cells.

Cell Surface Structures

Microvilli: specialized for absorption, covered in glycocalyx, and found in intestinal brush borders.
Stereocilia: found in epithelial cells of the male reproductive system, non-motile, with a core of actin filaments, important for ear sensory cells, and composed of fimbrin, villin, and espin.
Cilia: have a core of 9 microtubule doublets around two central microtubules (9+2), motile, and found in respiratory epithelium, oviduct, and uterine epithelium.
Axoneme: consists of a microtubule cytoskeleton, main extracellular part of cilia and flagella, and moves due to ATP hydrolysis catalyzed by dynein.

Cellular Adhesion Molecules (CAMs)

Transmembrane proteins, classified into Ca+2 dependent and Ca+2 independent types.
Ca+2 dependent:
- Cadherins: bind to similar proteins of the same tissue and with cytoskeleton filaments.
- Selectins: form weak intercellular connections, binding to specific oligosaccharide groups of glycoproteins and glycolipids.
- Integrins: glycoproteins that function as membrane receptors for ECM macromolecules, enabling cell aggregation and migration.
Ca+2 independent:
- Immunoglobulins (e.g., IgSF, ICAMs, NCAMs, E-CAMs, VCAMs), and Nectins, which establish weak hemophilic and heterophilic interactions.

Bone Cells

Osteocytes: mature bone cells housed in lacunae, contact each other via gap junctions, secrete sclerostin, IGF-1, and osteocalcin, and are nourished by nutrients diffusing from loose CT.
Osteoclasts: derived from bone marrow cells, localized in Howship's lacunae, specialized macrophages that perform bone resorption by creating an acidic environment and secreting proteolytic enzymes.
Osteoblasts: produce M-CSF, RANKL, and osteoprotegerin, which regulate osteoclast differentiation and bone resorption.

Immune Cells

Basophils: involved in allergic reactions, do not phagocytose, mediate hypersensitivity and anaphylactic reactions, and bind IgE via high-affinity FCER1 receptors.
Lymphocytes: agranulocytes, consisting of B and T cells, which are categorized into primary and secondary lymphoid organs.
Monocytes (Macrophages): contain azurophilic granules, have a high capacity for phagocytosis, belong to APCs, and secrete cytokines and biologically active compounds involved in inflammatory reactions.

Platelets and Blood Vessels

Platelets (Thrombocytes): fragments of megakaryocyte cytoplasm, important for stopping leaks in vessels (haemostasis), with alpha granules containing PDGF, PF4, fibrinogen, and plasminogen, and delta granules containing ADP, ATP, serotonin, and histamine.
Arteriovenous shunt: a wide direct communication between artery and vein.
Portal system: two capillary beds connected by a vein.
Lymphatic vessels: conduct immune cells and lymph to lymph nodes, remove excess fluid, and transport chylomicrons, not found in CNS, cartilage, or bone.

Heart

Valves: flaps of connective tissue anchored in the heart's dense fibrous skeleton.
Layers of heart's wall: endocardium, myocardium, and pericardium.
Impulse-conducting system: generated in the sinoatrial node, transmitted to the atrioventricular node, and then to the Purkinje fibers.

Glands Classification

Apocrine glands: secrete by apical portion of cytoplasm into a duct (e.g., mammary gland, lipid vacuoles)
Holocrine glands: secrete by shedding entire cells from the lining of the duct (e.g., sebaceous glands)
Simple glands:
- Simple tubular gland (e.g., interstitial glands of Lieberkühn)
- Simple coiled tubular gland (e.g., sweat gland)
- Simple tubular branched gland (e.g., glands of stomach and uterus)
- Simple acinar/alveolar gland (e.g., sebaceous glands of skin)
Compound glands:
- Compound tubular gland (e.g., glands of oral cavity)
- Compound acinar/alveolar gland (e.g., exocrine pancreas)
- Compound tubuloacinar gland (e.g., mammary gland)

Basement Membranes

Semipermeable filter formed of glycoproteins and other components
Two parts: basal lamina and reticular lamina (III collagen) bound to basal lamina by type IV collagen
Components: type IV collagen, laminin, nidogen, and perlecan

Cell Junctions

Tight Junctions (Zonulae Occludens):
- Present in apical part of cells
- Prevent free passage of substances between lumen of natural tract and basolateral intercellular space
- Proteins involved: occludins, claudins, JAMs (Junctional Adhesion Molecule), and Zonula Occludens proteins
Anchoring Junctions (Adherens Junction):
- Strong cellular adhesion and strength to tissues and strong cell-to-cell adhesion
- 3 forms:
  - Zonula adherens
  - Focal adhesions
  - Hemidesmosomes

Vessels

Elastic Artery (Aorta):
- Helps to reduce changes in blood pressure
- Has small vessels (vasa vasorum) and nerves in tunica adventitia and media
- Elastic membranes/Fenestrated membranes are in tunica media
- Tunica intima: endothelium with basal lamina, subendothelial connective tissues + smooth muscle, and internal elastic membrane
- Tunica media (thickest layer): multiple layers of fenestrated elastic lamellae, smooth muscle fibers
- Tunica adventitia: connective tissue, vasa vasorum + nerves
Muscular Artery:
- Tunica intima: endothelium + basal lamina, thin layer of subendothelial connective tissue, and internal elastic membrane
- Tunica media (thickest layer): many smooth muscle layers, less elastic material
- Tunica adventitia: connective tissue, thinner than media, vasa vasorum, maybe present
Arterioles:
- Subendothelial layer is very thin
- Elastic laminae are absent
- Tunica media: circularly arranged in 1-3 layers of smooth muscle cells
- Tunica adventitia: very thin, almost always branches to form networks of capillaries

Blood

Functions of Blood:
- Delivery of nutrients and oxygen to cells
- Transport of wastes and CO2 away from cells
- Delivery of hormones to and from cells and tissues
- Maintenance of homeostasis by acting as a buffer and participating in coagulation and thermoregulation
- Transport of humoral agents and cells of immune system that protects the body from pathogenic agents, foreign proteins, and transformed cells
Composition of Blood:
- Plasma:
  - Water (92%)
  - Proteins (7%): albumins, globulins, fibrinogen, regulatory proteins
  - Other (1%)
- Buffy Coat:
  - Platelets
  - Leukocytes: neutrophils, lymphocytes, monocytes, eosinophils, basophils
- Erythrocytes: anucleated and practically contain any organelles

Blood Cells

Anemia: concentration of erythrocytes or Hb below normal range (unable to receive adequate O2)
Erythrocytosis: increased concentration of erythrocytes in blood
Neutrophils:
- Function: to destroy invading microorganisms by phagocytosis and by secreting proteases and mediators of inflammation
- Cytoplasmatic granules
Basophils:
- Involved in allergic reactions
- They do not phagocytose
- Mediate hypersensitivity and anaphylactic reaction
- Bind IgE via high-affinity FCER1 receptors
Lymphocytes:
- Agranulocytes
- 2 categories: B lymphocytes (CD4, helper), T lymphocytes (CD8, cytotoxic)
- Primary lymphoid organs: bone marrow and thymus
- Secondary lymphoid organs: lymph nodes, spleen, and lymphoid aggregates of G1 and RT
Monocytes (Macrophages):
- Contain azurophilic granules
- Very high capacity to phagocytosis
- Belong to Antigen Presenting Cells (APCs)
- After 1-3 days, leave blood and become tissue macrophages
- After activation, secrete tens of cytokines and biologically active compounds involved in the inflammatory reaction
Platelets (Thrombocytes):
- Fragments of megakaryocytes cytoplasm
- Important role in stopping leaks in vessels (haemostasis)
- Alpha granules contain: PDGF, PF4, fibrinogen, plasminogen
- Delta granules contain: ADP, ATP, serotonin, histamine

Types of Joints

Synostoses: no movement, found in adults, example - skull bones
Syndesmoses: joins bones with dense connective tissue, example - interosseous ligament
Symphyses: thick pad of fibrocartilage, all symphyses occur in midline of body, examples - intervertebral discs and pubic symphysis
Diarthroses: free bone movement, examples - elbow and knee joints, characterized by a capsule enclosing a joint cavity containing synovial fluid

Cartilage

Cartilage is an avascular specialized fibrous connective tissue with a firmer ECM than that of CT proper
Functions: supports soft tissues, develops and grows long bones
Types of cartilage:
- Hyaline cartilage: type II collagen, example - trachea and bronchi
- Elastic cartilage: type II collagen and elastic fibers, example - epiglottis and cuneiform cartilage in larynx
- Fibrocartilage: type I and II collagen, example - intervertebral discs and pubic symphysis

Chondrocytes

Mature cartilage cells that are embedded within lacunae
Derived from mesenchymal chondrogenic cells and chondrogenic cells within the inner layer of perichondrium

Connective Tissue

Functions: supports other tissues and organs, acts as a medium for exchange of nutrients, protects against infectious agents, repairs damaged tissues, and stores fat (adipose tissue), Ca+2 (bone), and water (loose connective tissue)
Types of connective tissue:
- Embryonic connective tissue
- Connective tissue proper
- Specialized connective tissue

Extracellular Matrix (ECM)

Ground substance:
- Components:
  - Glycosaminoglycans (GAGs): made of uronic acid and hexosamine, resistant to compression
  - Proteoglycans (PGs): macromolecules with a protein core and GAGs attached
  - Adhesive glycoproteins: bind to components of ECM and to receptors of cell surface
Fibers:
- Collagen: type I, II, and III
- Elastic fibers

Fibroblasts

Function: produces and secretes collagen, plays an important role in wound repair
Types:
- Active fibroblast: basophilic, has well-developed RER and Golgi, relaxed chromatin, and many cell projections
- Inactive fibroblast (fibrocyte): acidophilic, has a small amount of RER and Golgi, condensed chromatin, and few cell projections

Macrophages

Functions: phagocytosis, antigen presentation to lymphocytes, secretion of cytokines
Types:
- M1: promotes inflammation, destruction of ECM, and apoptosis
- M2: anti-inflammatory, promotes rebuilding of ECM, proliferation, and angiogenesis

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Learn about different types of cell adhesions and junctions, including desmosomes, hemidesmosomes, and focal adhesions, and their roles in strengthening tissues and connecting cells to the basement membrane.