HISTO p3
• Delivers blood and substances to all tissues of the body.
Circulatory System
– lining epithelium, supporting layer of fibroelastic connective tissue
Endocardium
– contractile cardiac muscles arranged spirally around each chamber
Myocardium
– a simple squamous mesothelium supported by loose connective tissue layer containing blood vessels and nerves.
Epicardium
– thin fluid filled sac that surrounds the heart and large blood vessels that protects and lubricates the heart.
Pericardium
receives unoxygenated blood from the vena cava
right atrium
receives oxygenated blood from pulmonary veins
left atrium
delivers unoxygenated blood to the lungs
right ventricle
delivers oxygenated blood to the systemic circulation
left ventricle
• Dense irregular connective tissue
• Separates the musculature of the atria from that of the ventricles
• Forms part of the interventricular and interatrial septa
• Extends into the valve cusps and chordae tendinae
Cardiac skeleton
• Specialized epithelium that acts as a semipermeable barrier between blood and interstitial tissue fluid.
• Squamous, polygonal and elongated
Endothelium
• Provide non-thrombogenic surface on which blood will not clot and actively secretes anticoagulants
• Regulate local vascular tone and blood flow (stimulation of smooth muscle contraction or relaxation)
• Plays a role in inflammation and local immune response (WBC activation and activity)
Endothelium
- Present in the wall of all blood vessels that are larger than capillaries
• Arterioles: connected by gap junctions
• Permit vasoconstriction and vasodilation
Smooth Muscle fibers
– innermost layer
- Consist of endothelium and a thin subendothelial layer of loose connective tissue
Tunica Intima
– middle layer
- Consist chiefly of concentric layers of helically arranged smooth muscles
- Variable amounts of elastic fibers reticular fibers, and proteoglycans
Tunica media
- Connective tissue consisting primarily of Type I collagen and elastic fibers
Tunica adventitia/ Tunica externa
– carry oxygenated blood and nutrients from the heart to different tissues
Arteries
– Site of exchange of oxygen and nutrients
Capillaries
– carry unoxygenated blood and toxins from different tissues to the heart
Veins
• Aorta, pulmonary artery and their largest branches
Elastic Arteries
– role to carry blood to smaller arteries.
“Conducting arteries”
• Monitor blood arterial pressure
• Carotid sinuses
• Aortic arch
• Thinner tunica media
• ↑ free nerve endings in the tunica adventitia
Baroreceptors
• “Distributing arteries”: distribute blood to organs
• Regulate BP by contracting or relaxing its smooth muscles.
Muscular Arteries
• Branches of muscular arteries
• Smallest arteries: microvasculature of the organs where exchanges between blood and tissue fluid occurs.
Arterioles
• Allow and regulate metabolic exchange between blood andsurrounding tissues.
• Simple layer of endothelial surrounded by basementmembrane.
• Size allows transit of blood cells one at a time
Capillaries
– mesenchymal cells that surround the capillaries
• Dilate and constrict the capillaries through a well-developed myosin, actin, and tropomyosin
• Regulate blood flow in some organs
• Proliferate and differentiate after an injury →formation of smooth muscles and other cells in new vessels as microvasculature is reestablished.
Pericytes
• Connected to capillaries, and with larger pericytes
• Primary site where WBCs adhere to endothelium and leave the circulation at site of infection
• Large collapsed lumen
Venules
• Delivers blood from tissues to the heart
• Movement of blood:
• contraction of smooth muscles in the wall of the veins
• External compressions from surrounding muscles
Veins
• Network of small thin-walled channels
• Collect excess interstitial fluid from tissue spaces as “lymph” and return it to the blood.
• Movement of lymph is aided by external forces
• Unidirectional flow is maintained by valves
Lymphatic System
• Simple endothelium that lacks tight junctions and rest on a discontinuous basal membrane
• Smooth muscle and connective tissue cells
• No distinct layers of tunics
• Lymphatic vessels
• Formation of a fibrin mesh by the activation of the coagulation cascade
Blood Coagulation
• Clot initially buldges into the blood vessel lumen, but soon contracts due to the activity of platelet derived actin and myosin
Clot formation
• Endothelium and surrounding tissue are restored
• The clot is removed by the activation of Plasmin
Clot removal
• Includes sweat glands, sebaceous glands, and coarse moist vibrissae (hairs)
• Looses keratinization and transition from stratified squamous epithelium to pseudostratified columnar epithelium
Vestibule
• Lies within the skull as two cavernous chambers separated by osseous nasal septum
• Conchae or turbinate bones extends from each lateral walls
• Lined by pseudostratified columnar epithelium
• Underlying loops of capillaries for warming inspired air
Nasal Cavity
– humidifies inspired air and mucus traps particulate and air impurities
Seromucous glands
• most abundant, each with 250-300 cilia on its apical surface
Ciliated Columnar Cells
• numerous and predominate in some areas, with basal nuclei and apical domains filled with granules of mucin glycoproteins.
Goblet Cells
• less numerous, columnar cell type, in which a small apical surface bears sparse, blunt microvilli.
Brush Cells
– resembles gustatory cells, with similar transduction components and synaptic contact with afferent nerve endings on their basal surfaces.
Chemosensory receptors
– resembles gustatory cells, with similar transduction components and synaptic contact with afferent nerve endings on their basal surfaces.
Chemosensory receptors
• Contains numerous granules
• Like endocrine cells of the gut, the are part of the Diffuse Neuroendocrine System (DNES)
Small Granule Cells (Kulchitsky Cells)
• mitotically active stem and progenitor cells that give rise to the other epithelial cells
Basal Cells
• Thick Pseudostratified Columnar Epithelium
• Chemoreceptors for the sense of smell.
• Covers the superior conchae at the roof of the nasal cavity
• Lamina propria possess large serous glands, Olfactory Glands (of Bowman), which produce constant flow of fluid surrounding the olfactory cilia and facilitating access of new odoriferous substances.
Olfactory epithelium
• bipolar neurons present throughout the epithelium.
• Apical pole is its dendrite end and has a knob-like swelling with dozen basal bodies from which long cilia project into the overlying aqueous layer.
• Cilia provides large surface for transmembrane chemoreceptors
• Responds to odoriferous substances by generating an action potential along the axons extending from the basal ends.
• Enters the brain through a foramina in the cribriform plate as Cranial Nerve I (Olfactory Nerve)
Olfactory Neurons
• columnar cells with narrow bases and broad cylindrical apexes containing the nuclei and extending microvilli into the fluid layer.
• Well developed junctional complexes bind the supporting cells to the olfactory cells.
• Express ion channels which help maintain a microenvironment conductive to olfactory function and survival.
Supporting Cells
– small spherical or cone-shaped cells near the basal lamina.
• Stem cells for the other two types of cells
• Replaces the olfactory neurons every 2-3 months
• Replaces support cells less frequently.
Basal Cells
• Bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull.
• Lined with a thinner respiratory epithelium having fewer goblet cells.
Paranasal sinuses
• Nasal cavities open posteriorly into the Nasopharynx, the first part of the .
• Nasopharynx is continuous caudally with the oropharynx, the posterior part of the oral cavity leading to the larynx and esophagus.
• Connected to each middle ear cavity through the auditory tubes
Pharynx
• A short passage for air between the pharynx and the trachea
Larynx
• Lined with typical respiratory epithelium (Ciliated Pseudostratified Columnar Epithelium)
• Lamina propria: numerous sero-mucinous glands producing watery mucus.
Trachea
• located between the submucosa and adventitia
• Maintains the shape of trachea and keeps it open
C-shaped cartilages
• Consist of a bundle of smooth muscle tissues
• Relaxes during swallowing to allow passage of food
• Allows the esophagus to bulge into the lumen of the trachea
Trachealis muscle
• Distal branches of Respiratory Bronchioles
• Lined completely by the openings of alveoli (extremely attenuated squamous cells).
Alveolar ducts
• Large clusters of alveoli that forms the ends of alveolar ducts distally
• Lamina propria contains
Alveolar sacs
• Sac-like evaginations from the respiratory bronchioles, alveolar ducts and alveolar sacs
• Responsible for the spongy structure of the lungs
• Each alveoli resembles a rounded pouch open on one side to an alveolar duct or alveolar sac.
Alveoli
• Lies in between two alveoli
• Consist of scattered fibroblasts and ECM (elastic and reticular fibers)
Interalveolar septa
enables alveoli to expand with inspiration and contract passively with expiration
Elastic Fibers
• prevent both collapse and excessive distention of alveoli
• Vascularized with a network of capillaries
Reticular Fibers
• 2-3 highly attenuated, thin cells lining the alveolus
• Fused basal lamina of the lining cells and the endothelial cells of capillaries
• Thin capillary endothelial cells
Blood-Air Barrier
• Penetrate the interalveolar septa and connects neighboring alveoli that open to different bronchioles
• Equalize air pressure in the alveoli and permit collateral circulation of air if a bronchiole becomes obstructed
Alveolar Pores
• Found within the alveoli or in the interalveolar septum
Alveolar Macrophages (Dust Cells)