Columnar cells types

The highly vascularized respiratory epithelium is composed of five major cell types ciliated cells, nonciliated cells, columnar cells, goblet cells, and basal cells. Low numbers of neurosecretory cells are present in the basement membrane [17]. Approximately 20% of the total number of cells in the lower turbinate area is ciliated with fine projections ( 100 per cell) on the apical cell surface. Cilia are used to transport the mucus toward the nasopharynx. These long (4-6 fxm) and thin projections are mobile and beat with a frequency of 1,000 strokes per min. Ciliated and nonciliated columnar cells are populated with about 300 microvilli per cell, which help in enlarging the surface area. 

Figure 10.1 Typical tracheo-bronchial and bronchiolar epithelia showing the major cell types. The tracheo-bronchial epithelium showing the pseudostratified nature of the columnar epithelium, principally composed of ciliated cells (C), interspersed with goblet cells (G), brush cells (Br), serous cells (S), Kulchitsky s cells (K) and basal cells (B). The bronchiolar epithelium showing the cuboidal nature of the epithelium, principally composed of ciliated cells (C), Clara cells (Cl) and infrequent basal cells. Muc = mucus Ci = cilia N = nucleus Sec = secretory granules.

The epidermis consists of several types of cells. The epidermal cell type apposed to the dermis is the stratum germinativum (basal cell layer), over which are the stramm spinosum, stratum granulosum, stratum ludicum, and the outermost layer or stratum corneum. The basal cell layer consists of one layer of columnar epithelial cells. On division, the basal cells are pushed up and become the stratum spinosum, which consists of several layers of cells. As these cells approach the surface of the skin they become larger and form the stratum granulosum. 

The pharynx, larynx, trachea and bronchi are lined with pseudostratified, ciliated columnar epithelium that contain at least eight cell types, including mucous secretory goblet and Clara cells, which produce a protective mucus layer of 5-10 jum thickness (see Table 9.2). Subepithelial secretory glands, present in the bronchial submucosa, also contribute to the mucus blanket [9]. Through coordinated ciliary movement a propulsive wave is created, which continuously moves the mucus layer up towards the larynx. Consequently, the mucosal surface of trachea and bronchi is constantly swept to remove inhaled materials. As the bronchi divide into bronchioli, the ciliated columnar respiratory epithelium is much thinner and changes to a simpler non-ciliated cuboidal epithelium. The epithelium in the terminal and respiratory bronchioles consists of ciliated, cuboidal cells and a small number of Clara cells. However, Clara cells become the most predominant type in the most distal part of the respiratory bronchioles [10]. 

Figure 9.2 Diagram of the four cell types in the nasal respiratory epithelium. A ciliated columnar cell covered by cilia and microvilli of uniform length B basal cell C goblet cell packed with mucus granules D nonciliated columnar cell, covered by microvilli of uniform length. (Redrawn from Mygind, N., 1979 Nasal Allergy, 2nd edition. Blackwell Scientific Publications Oxford).

In some cases, cells in a persistently stressful environment may be replaced by a cell type that is better able to withstand the harsh environment. Replacement of an adult cell type by another adult cell type is known as metaplasia and is usually a reversible change. Perhaps the best-known example of metaplasia is the replacement of the normally tall (columnar), ciliated epithelial cells in the respiratory tract of cigarette smokers by layers of relatively flattened (squamous) epithelial cells. While the squamous epithelial cells are somewhat tougher than the columnar cells, important functions such as mucus secretion are lost. In addition, the continued stresses that induce metaplasia may lead to neoplastic transformation. 

Fig. 1 (A) Cross-sectional structure of the human nose. NV = nasal vestibule AT = atrium NP = nasopharynx IT = interior turbinate and orifice of the nasolacrimal duct MT = middle turbinate and orifices of frontal sinus, anterior ethmoidal sinuses, and maxillary sinus ST = superior turbinate and orifices of posterior ethmoidal sinuses hatched area, olfactory region. (B) Four major cell types in the nasal epithelium (a) non-ciliated columnar cell with microvilli (b) goblet cell with mucous granules and Golgi apparatus (c) basal cell and (d) ciliated columnar cell with many mitochondria in the apical part. (Reprinted from Ref. with permission from Elsevier.)...

Mucous Surface. The mucosa of the small intestine consists of three layers (Fig. 2) an absorptive layer, a continuous single sheet of columnar epithelium the lamina propria, a layer heterogeneous in composition and cell type and the muscularis mucosa, a muscular layer separating the mucosa and submucosa. 

The mammalian epididymis is a highly coiled duct where sperm undergo maturation and are stored prior to ejaculation. The epididymis is comprised of a head (caput), a body (corpus), and a tail (cauda), which can be defined by their relative location, tissue characteristics, and cell types. Within a connective tissue sheath, the epididymis is a complex of tubules lined with columnar epithelial cells attached to a basement membrane. Epithelial cell height decreases and luminal diameter increases from the initial segment to the cauda of the epididymis. There are several distinct epithelial cell types found in the mammalian epididymis, including the principal, narrow, basal, clear, and halo cells. The principal cells... 

A monolayer of multiple cell types comprises the intestinal epithelium. Entero-cytes, the absorptive cells, are the main focus in drug delivery issues. In addition to enterocytes, there are undifferentiated crypt cells, mucus-secreting goblet cells, and M cells, which sample the gut lumen for the lymphatic system.6 However, it is the columnar villar enterocyte that forms the primary barrier to absorption. An extensive network of microvilli on the apical surface of villar enterocytes provides a vast amount of surface area for absorption of nutrients, pharmaceuticals, and xenobiotics.6,7... 

Columnar cells are longer than they are wide the small intestine is a tubular organ lined with a simple columnar epithelium composed of a single layer of cells. Unicellular glands are scattered throughout this type of tissue and secrete mucus. 

Another recently proposed classification system, which pertains mainly to adenoma in the EHBDs, divides them into two categories on the basis of the predominant cytologic features columnar-cell and cuboidal-cell types." This is analogous to the villous/intestinal and pancreatobiliary subsets of pancreatic IPMNs, respectively. ... 

Cytokeratins (CKs) are a family of intracytoplasmic intermediate filament proteins present in almost all epithelia. Expression of each CK molecule depends on cell type and differentiation status, and therefore specific CKs can be used as markers to identify particular types of epithelial tumors (Table 16.5). CK7 is found in a wide variety of epithelia including the columnar and glandular epithelium of the lung, cervix, and breast, as well as in the bile duct, collecting ducts of the kidney, urothelium, and mesothelium, but not in most gastrointestinal epithelium, hepatocytes, proximal and distal tubules of the kidney, and squamous epithelium. In contrast, CK20 shows relatively restricted expression and is present in gastrointestinal epithelium, Merkel cells of the epidermis, and urothelium. 

The epithelial basal cell is characterized by its small amount of cytoplasm in relationship to its relatively large nucleus. It is present mainly in large airways and is believed to be the stem cell or precursor cell of the tracheal epithelium and able to differentiate into other epithelial cell types. The intermediate cell, which is columnar and extends from the basement mem-... 

In the cervix, HPV infects epithelial cells that lie under the mucosal membrane (see Figure HPV-4). The types most responsible for cervical cancer, HPV 16 and 18, make proteins that bind to two tumor suppressors, one of which is p53, which we saw in Chapter 24. This allows the endothelial cells to divide abnormally. Cancer occurs for reasons still not well understood when the abnormal endothelial cells contact the columnar cells. 

The liver is the first organ to receive blood that contains glucose absorbed from the intestine. The portal vein drains from the small intestine into the hepatic sinuses that are surrounded in a neat columnar fashion by hepatocytes. The arrival of glucose in the blood is detected by the p-cells in the pancreas, and they respond by secreting the peptide hormone insulin. Insulin facilitates glucose uptake by many cell types, from skeletal muscle to white blood cells (Fig. 11-4), but it has no effect on glucose uptake by the brain or red blood cells that rely on GLUT-1. 

Columnar cells with nuclei at varied distances from the luminal border were distinguished throughout fetal development, as in adults. Functional interpretation of these cells is beyond the scope of this study. However, columnar cells of different morphological types have been described previously in adults, and certain columnar cells (with short microvilli) have been suggested as potential receptors (Moran et al., 1991, 1995). Further investigation is clearly needed on the apical characteristics of VNO columnar cells. For example, the present investigation and some previous studies (Johnson et al., 1985 Sten-saas et al., 1991) have noted some cilia in the adult human VNO. The precise distribution of these ciliated cells is important, since the non-sensory, receptor-free epithelium of the VNO of other mammals (Briepohl et al., 1979) also possess cilia. 

---