Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
David W. Hobson in Dermal and Ocular Toxicology, 2020
In man, the integument is derived from two morphologically distinct layers: the epidermis from surface ectoderm and the dermis from mesoderm. The surface ectodermal cells proliferate in the second month to form the periderm (epitrichium). This cell layer consists of simple squamous epithelium with microvilli, which increases the epidermal surface area exposed to the amniotic fluid. The presence of microvilli on the amniotic surface suggests that the periderm cells are involved in the exchange of material between the fetus and amniotic fluid. The peridermal cells contain filaments and glycogen and the underside is attached by junctional complexes to the adjacent epithelial cells. The basal ectodermal cells continue to proliferate and undergo keratinization and desquamation. These exfoliative cells, along with sebum from the sebaceous glands and other cellular debris, form the vernix caseosa, a whitish protective substance that covers the fetal skin. At birth, all cell layers are present.29–32 Cells of neural crest origin migrate into the epidermis during the early fetal period. Breathnach and Wyllie33 noticed melanocytes and Langerhans’ cells at 14 weeks in human fetal epidermis.
The respiratory system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
The respiratory bronchioles are lined with nonciliated cuboidal epithelial cells that gradually flatten and become squamous type cells. As mentioned previously, the alveoli are composed of large, flat, simple squamous epithelium.
Cells, Tissues and Organs
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
Columnar (column-like) cells are typically found in the lining of the stomach and digestive tract where they absorb and secrete a number of substances/molecules. They are also found in the nose, ear and tongue (taste buds) where they help to transmit sensory information towards the brain. ‘Goblet cells’ are specialist columnar epithelium that secrete mucin, a substance that dissolves in water to produce mucus (picture a goblet of mucus). Others are covered in fine hair-like structures called cilia (ciliated epithelium). These are capable of rapid, rhythmic wafting in order to propel mucus out of the respiratory tract or, in the case of those found in the female reproductive tract, they waft the egg cell (ovum) along the fallopian tube towards the uterus (see Chapter 14). Cuboidal (cube-like) epithelial cells are often found in glandular (secretory) tissue and in the lining of the tubules of the kidney (nephrons). They also make up the germinal cells which produce the ova in the female ovary and the sperm in the male testes. Finally, squamous (flat) epithelial cells make up the outer layer of the skin and line a number of cavities and internal structures including the mouth, blood vessels, cervix and lungs. You may have heard of squamous cell carcinoma which refers to a type of cancer or neoplasm that derives from these cells. Examples include skin cancer, some forms of lung cancer and the most common type of cervical cancer. Epithelial cells can also be classified in terms of their structure or arrangement. They can be simple (in a single layer), stratified (one on top of the other – in strata) or pseudo-stratified (in a single layer but appear to be stratified). For example, simple squamous epithelium can be found on the inside of blood vessels or lining the air sacs (alveoli) of the lungs. This simple arrangement allows rapid diffusion of gases such as oxygen and carbon dioxide between cell membranes. Stratified squamous epithelia, on the other hand, are found in the cornea of the eye or lining the oral (mouth) cavity. Stratified epithelium is well suited to areas of the body that are subject to abrasion since the layers can be shed and quickly replaced before the basement membrane is exposed.
Effects of catechin hydrate in benzo[a]pyrene-induced lung toxicity: roles of oxidative stress, apoptosis, and DNA damage
Published in Toxicology Mechanisms and Methods, 2021
Samah A. Khattab, Wafaa F. Hussien, Nermin Raafat, Eman Ahmed Alaa El-Din
In control animals, H&E-stained sections of lung tissues showed a lace appearance as most lung tissues composed of thin-walled alveoli. The alveoli are composed of a single layer of squamous epithelium. A thin layer of connective tissue and numerous capillaries also lined with simple squamous epithelium was found between the alveoli. Also, corn oil and DMSO groups showed the same appearance. While (group IV) B[a] P-treated rats showed abnormally thick alveolar walls and a markedly congested blood vessel with interstitial pneumonia in the form of thick alveolar walls. Most alveoli appeared empty air-filled alveoli, and severe mononuclear inflammatory infiltrates restricted to the alveolar walls and interstitial tissues. Lung tissue from rats treated with B[a] P + CH (group VI) revealed mild congestion of the alveolar capillaries with thickened edematous alveolar walls infiltrated but with few inflammatory cells. While group V treated with CH only appeared normal with thin-walled alveoli with normal squamous epithelium. A thin layer of connective tissue and numerous capillaries lined with simple squamous epithelium (Figure 2).
Chronic effects of maternal tobacco-smoke exposure and/or α-lipoic acid treatment on reproductive parameters in female rat offspring
Published in Systems Biology in Reproductive Medicine, 2020
Elif Erdem Guzel, Nalan Kaya, Ahmet Tektemur, Nazife Ulker, Ahmet Yardimci, Ramazan Fazil Akkoc, Sinan Canpolat, Ibrahim Enver Ozan
Ovaries were fixed in 10%-buffered formaldehyde, and then embedded in paraffin. Samples were cut at 5 µm thicknesses and stained with hematoxylin and eosin (H&E) by a light microscope (NovelN-800 M, Ningbo, China). Follicles were identified as healthy if they had a solid oocyte and contained organized layers of granulose and thecal cells. The follicles were considered atretic if they had a degenerate oocyte and granulosa cells with pycnotic nucleus poured into the lumen around the oocyte. Follicular cysts (FC) were identified fluid-filled pockets of ovaries that formation within a secondary follicle. The surrounding zona granulosa was attenuated. The cyst cavity was lined by a simple squamous epithelium. The severity of damage in the ovarian tissue was evaluated semiquantitatively in terms of the specified changes; inflammatory cell number, vascular congestion, germinal epithelial degeneration, follicular degeneration (follicle cell loss + follicular fluid increase), atretic and cystic follicle, vacuolization in granulosa cells and corpus luteum. Histoscores were given as 0 = absent, 1 = weak, 2 = moderate and 3 = strong for each parameter (Mazaud et al. 2002). All histological evaluations were performed by two blinded investigators.
Ameliorative role of alpha-lipoic acid in renal cortical structural damage, induced by limb ischemia-reperfusion injury in the rat
Published in Ultrastructural Pathology, 2022
Manal A. Othman, Heba A Mubarak, Manal M. Sayed
Group I: Histological examination of semithin sections, stained with toluidine blue, from control rats, revealed proximal convoluted tubules (PCT) demonstrating normal cytoplasmic features, and typical vesicular nuclei. The distal convoluted tubules (DCT) appeared with their wider lumen. The renal corpuscles, with its Bowman’s capsule, had a parietal layer of simple squamous epithelium, and inner layer of podocytes. The glomerular capillaries appeared normal with normal spaces (Figure 1A). Examination of group II (ischemia-reperfusion after 1 day) revealed that PCT had variable cytoplasmic vacuolizations. DCT showed vacuolated cytoplasm and dark nuclei. Renal corpuscle showed atrophic glomeruli, wide urinary spaces (Figure 1B). In group III (ischemia-reperfusion after 7 days) the PCT had marked vacuolizations and loss of brush border. DCT revealed dark pyknotic nuclei and cytoplasmic vacuolizations. Renal corpuscle showed marked glomerular atrophy, wider urinary space, and darker cellular nuclei (Figure 1C). On the other hand, examination of group IV (ischemia-reperfusion after lipoic acid treatment) revealed improvement in the cellular architecture; most PCT and DCT were within near normal morphology but few of them showed vacuolated cytoplasm. The renal corpuscle showed more or less normal appearance (Figure 1D).
Related Knowledge Centers
- Basal Lamina
- Basement Membrane
- Diffusion
- Epithelium
- Filtration
- Mesothelium
- Peritoneum
- Endothelium
- Capillary
- Pulmonary Alveolus