Cardiovascular physiology
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
The liver blood flow is one-quarter of the cardiac output and is from the portal vein and the hepatic artery. The portal vein normally accounts for three-quarters of the blood supply, but the hepatic artery provides three-quarters of the oxygen consumed by the liver. The hepatic lobule – the basic histological unit – consists of a central hepatic efferent venule with cords of hepatocytes and sinusoids converging onto the efferent venule (see Chapter 6). The acinus is the functional unit and consists of a parenchymal mass between two centrilobular veins, and it is supplied by terminal branches of the hepatic artery and portal veins, which drain into the sinusoids and then into the hepatic venules. The sinusoids form a low-pressure microcirculatory system of the acinus with sphincters at the hepatic arteriole, hepatic venous sinusoid and arteriolar–portal shunts. Thus, the sinusoids act as a significant blood reservoir depending on the sphincters’ tone, which is determined by sympathetic nerve activity. The mean blood pressure is 10 mmHg in the portal vein, 90 mmHg in the hepatic artery and 5 mmHg in hepatic veins. Blood reaches the sinusoids at a pressure less than 10 mmHg because the hepatic arterioles have a high resting tone, controlled by local myogenic and metabolic factors and by extrinsic sympathetic nerve control. If blood flow in the portal vein falls (or liver metabolic activity increases), local metabolic control increases hepatic artery flow (up to 50% of total liver blood flow). If blood flow in the portal vein rises, local myogenic control reduces hepatic artery flow.
Hepatotoxins
John F. Pohl, Christopher Jolley, Daniel Gelfond in Pediatric Gastroenterology, 2014
Histologically, hepatotoxins may injure the liver differentially. The hepatic acinus is the functional unit of the liver and is oriented around the afferent vascular system. The acinus consists of an irregular shaped, roughly ellipsoidal mass of hepatocytes aligned around the hepatic arterioles and portal venules just as they anastomose into sinusoids. The acinus can be divided into zones that correspond to the distance from the arterial blood supply (39.4). Hepatocytes closest to the arterioles (zone 1) are the best oxygenated, while those farthest from the arterioles have the poorest supply of oxygen (zone 3). This arrangement also means that cells in the center of the acinus (zone 1) are the first to be exposed to blood-borne toxins absorbed into portal blood from the small intestine. Zonal patterns of injury may or may not be specific to the toxin.
Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
Sebaceous glands can be associated with terminal or vellus hair fibers. In terminal hair, the sebaceous duct opens into the hair follicle canal. In vellus hair, the hair follicle canal and the acini of the sebaceous gland are in close proximity and lead into a principal hair follicle canal. The anatomical distribution of sebaceous glands is unique inasmuch they are not found in the palms of the hands and soles and dorsum of the feet.48 The size and density of the glands also depend on anatomical location.49 For example, the facial region contains the largest glands and the highest density of sebaceous glands is found in the scalp, forehead, face, and anogenital region.50,51 Sex and age are also determinant factors in the size and density of sebaceous glands. The morphological structure of the sebaceous gland consists of several-to-many acini, which contain sebaceous cells. As illustrated in Figure 1.14, the acini are located at the base of the gland and lead into a duct, which eventually makes its way to the hair follicle canal.
Bioidentical hormones
Published in Climacteric, 2021
F. Z. Stanczyk, H. Matharu, S. A. Winer
Saliva is a complex fluid which is mostly produced by the parotid, submandibular, and sublingual salivary glands, with a small contribution from the buccal glands that line the mouth13. In addition, saliva contains variable amounts of gingival crevicular fluid, which leaks from the tooth–gum margin, or blood from oral abrasions or lesions. Steroid hormones can enter saliva by a variety of mechanisms but for most steroids the most common route is rapid passive diffusion through the acinar cells, which drain into the salivary ducts13. The acini are surrounded by blood capillaries that enable the passage of substances from the circulation into the salivary glands. In passive diffusion, lipid-soluble substances such as progesterone and E2 cross the cell membranes of capillaries and acini rapidly. It is only the non-protein-bound steroids that enter the acini; steroids bound to sex hormone-binding globulin (SHBG), corticosteroid-binding globulin (CBG) and albumin are too large to enter acinar cells.
Vitamin E protects against the modulation of TNF-α-AMPK axis and inhibits pancreas injury in a rat model of L-arginine-induced acute necrotising pancreatitis
Published in Archives of Physiology and Biochemistry, 2023
Fahaid Al-Hashem, Mohamed Abd Ellatif, Asmaa M. ShamsEldeen, Samaa S. Kamar, Bahjat Al-Ani, Mohamed A. Haidara
In view of the results described above that showed substantial protection by vitamin E to L-arg-modulated biomarkers of inflammation, pancreatic tissue necrosis, AMPK, and leukocyte infiltration, we investigated whether vitamin E can also protect pancreatic tissue against injury induced by L-arg in a rat model of acute pancreatitis using morphological and histological investigations. Thus, explanted pancreases from all animal groups were examined and tissue samples were prepared for basic histology staining. Compared to normal macroscopic images in the control groups of rats (Figure 5(A), I and data not shown), L-arg induced swelling with patchy areas of haemorrhage (Figure 5(A), II). Vitamin E treatment (Figure 5(A), III) substantially but not completely preserved the pancreas morphological structure. Representative H&E images of the pancreatic tissue obtained from the control groups of rats (Figure 5(B), I and data not shown) show the regular architecture of pancreatic tissue as demonstrated by multiple lobules separated by thin connective tissue (CT) septa, with each lobule forming multiple acini lined with pyramidal cells. These cells show basal rounded pale nuclei, basal basophilic cytoplasm, and apical acidophilic granules. H&E image represents pancreatic sections of the model group (L-arg) of rats (Figure 5(B), II) which shows disorganised lobular architecture with inflammatory infiltration within the CT septa. The acini appear with multiple cytoplasmic vacuolations and pyknotic nuclei. In addition, the presence of congested blood vessels and extra-vasated blood in between the acini are revealed.
Predictions of inter- and intra-lobar deposition patterns of inhaled particles in a five-lobe lung model
Published in Inhalation Toxicology, 2021
Renate Winkler-Heil, Majid Hussain, Werner Hofmann
The probability that a given air volume element enters an alveolus is randomly selected from the ratio of the flow into the alveoli of a given acinar airway to the total flow entering that airway. The flow into an alveolus depends on the difference of alveolar volumes between the contracted and expanded state, which is determined by the inflated and deflated alveolar diameters, multiplied by the degree of alveolization in that generation (Weibel 1963). The minimum alveolar diameter representing the deflated state of an alveolus at the end of expiration is assumed to be 233 µm, which increases to 250 µm at the end of inhalation under resting breathing conditions (Balásházy et al. 2008). The relationship between alveolar expansion and physical activity is modeled by a linear function, starting from a maximum alveolar diameter of 250 µm for resting breathing conditions (VT = 750 mL) up to a maximum diameter of 273 µm for heavy exercise (VT = 1923 mL) (Balásházy et al. 2008).
Related Knowledge Centers
- Exocrine Gland
- Lung
- Stomach
- Scalp
- Cell
- Berry
- Raspberry
- Pulmonary Alveolus
- Sebaceous Gland
- Salivary Gland