Here is one scientific article that was rewritten so that it is more easily understood by a non-scientist as it is filled with scientific terms and descriptions. I feel that it is highly significant and is a must read for your repertoire of understanding the penis collagenous structure.
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Abstract. The tunica albuginea of the corpora cavernosa is a bi-layered structure with multiple layers. Inner layer bundles support and contain the cavernous tissue and are oriented circularly. Radiating from this layer are intracavernous pillars acting as struts, which augment the septum (make (something) greater by adding to it) increase ( and provide essential support to the erectile tissue. The septum is originates from the inner circular layer of collagen coming together to form a wall thus dividing the corpus cavernosum into two chambers. Outer layer bundles are oriented longitudinally or lengthwise orientation to the shaft. These fibers extend from the glans penis to the proximal crura, where they insert into the inferior pubic ramus. There are no outer layer fibers between the 5 and 7 o'clock positions. Elastic fibers normally form an irregularly latticed network on which collagen fibers rest. In Peyronie's disease the well ordered appearance of the collagen layers is lost: excessive deposits of collagen, disordered elastic fibers and fibrin are found within the region of the plaque.
Collagen Fiber Alignment. The human tunica albuginea is a complex structure, and is designed to be functionally compatible for the purpose of sexual intimacy. The collagen bundles are oriented either circularly or longitudinally with multiple collagen bundle layers able to slide against each other .The inner layer of collagen is finer, and has circularly oriented bundles which surround and penetrate the cavernous tissue. The coarser outer layers are directed longitudinally extending from the base to the glans. The overall shape of the penis varies, with the location determined by the surrounding tunica albuginea.
Septum and Corpus Cavernosum. The septum dividing the two chambers of the corpus cavernosum (cc) is formed from the inner layer bundles. The median septum is complete proximally (the base area) and extends distally into each crus (areas of attachment) and are often incomplete at the glans. The inner layer bundles also send off perpendicular or intracavernous pillars that act as struts analogous to spokes on a bicycle Figure 2. The struts maintain intracavernous support.. The dorsal aspect (top) is fenestrated (having fenestrae or windowlike openings). In summary, the inner layer has circular bundles that send off projections into the septum and thickened regions at the 6 o'clock position that represent the coalescence of bundles from both sides.1
Figure 2 Intracavernous pillars between approximately 6 and 2 o'clock position. Note striation. Reduced from X25. Reprinted with permission. [5]
Ventral (bottom) thickenings. The outer layer bundles oriented longitudinally (along the length of the shaft from base to glans)condense to form triangular ligamentous structures that we call ventral thickenings at the 5 and 7 o'clock position Figure 1. The intervening space (the ventral groove) houses the corpus spongiosum. Absence of longitudinal bundles between the ventral (bottom) thickenings allows the corpus spongiosum (cs) to expand without restriction.
Longitudinal band thickenings toward the glans. Note that the longitudinal bundles are thicker on top (dorsally) these dorsal (top) thickenings bands are located at the 11 and 1 o'clock positions and ultimately extend into the glans distally as a single structure. These longitudinal bundles are located in the glans at the 12 oclock position.
Dorsal thickenings at the base. When the dorsal thickenings are followed toward the base (proximally), they form the walls of the dorsal groove Figure 1, then gradually separate, anchoring the penile crura to the inferior pubic ramus. The longitudinal fibers from the lateral (side) aspect (1 to 4 and 8 to 11 o'clock positions) interdigitate with the suspensory ligament and fan out to join the adjacent ischiocavernous muscle (very important concept!).
Summary Thus Far. Hence, a circumferential ligamentous structure composed of ventral (bottom) and dorsal (top) thickenings and the lateral (sides) bundles is created, anchoring the penis to the ischial tuberosity (section of the hip bone behind the penis structure) immediately ventral to the pudendal nerve (one of the main nerve tracts coming from the sacral spine area) while providing the cavernous tissue with structural support.
Role of Elastic Fiber Mesh. The second structural component of the tunica albuginea is the elastic fibers that form an irregularly latticed framework on which collagen rests Figure 3A &B. In the penile shaft tunical elastic fibers and collagen are intertwined. However, proximally (the base) strands of skeletal muscle intermingle with outer layer bundles along the lateral aspect of the crus penis (interface of collagen fibers and IC muscle). The elastic network is present but with fewer fibers. The tunica at both ends (base and glans) where the inner layer bundles terminate, consists exclusively of collagen, reminiscent of ligamentous tissue.
Collagen Metabolism
In this article, I have printed the abstract and introduction with the article figures 1,2, and 3. I felt it unnecessary to rewrite it as it is relatively easy to read and can be accessed free. Unfortunately I was unable to produce a clearer illustration of Figure 2. You can access at no cost this paper in its entirety from
Medscape: Medscape Access [3]
Abstract. The process of wound healing consists of an orderly sequence of events characterized by the specific infiltration of specialized cells into the wound site. The platelets and inflammatory cells are the first cells to arrive, and they provide key functions and signals needed for the influx of connective tissue cells and a new blood supply. These chemical signals are known as growth factors or cytokines. The fibroblast is the connective tissue cell responsible for collagen deposition needed to repair the tissue injury. Collagen is the most abundant protein in the animal kingdom, as it accounts for 30 percent of the total protein in the human body. In normal tissues, collagen provides strength, integrity, and structure. When tissues are disrupted following injury, collagen is needed to repair the defect and hopefully restore structure and thus function. If too much collagen is deposited in the wound site, normal anatomical structure is lost, function is compromised, and the problem of fibrosis results. Conversely, if insufficient amounts of collagen are deposited, the wound is weak and may dehisce. Therefore, to fully understand wound healing, it is essential to understand the basic biochemistry of collagen metabolism.
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Introduction. Collagen is found in all of our connective tissues, such as dermis, bones, tendons, and ligaments, and also provides for the structural integrity of all of our internal organs.[1,2] Therefore, because of its wide distribution throughout our bodies, it represents one of the most abundant naturally occurring proteins on earth.[3] In addition to its natural abundance, there are well over 1,000 commercial products on the market today that contain collagen and collagen enhancers. These products are represented by body and hand lotions, nail treatments, firming gels, wrinkle injections, eye pads, and even anti-cancer treatments to name but a few. In recent years, new high-tech wound dressing materials and skin substitutes have become available for the treatment of partial-thickness injuries as well as full-thickness and chronic dermal ulcers.[2]
There are close to 20 different types of collagen found in our bodies.[4,5] Each one of these collagens is encoded by a specific gene. The five major types are summarized in Table 1 . The predominant form is Type I collagen. This fibrillar form of collagen represents over 90 percent of our total collagen and is composed of three very long protein chains. Each protein chain is referred to as an "Alpha" chain. Two of the Alpha chains are identical and are called Alpha-1 chains, whereas the third chain is slightly different and is called Alpha-2. The three chains are wrapped around each other to form a triple helical structure called a collagen monomer (Figure 1). This configuration imparts tremendous strength to the protein. To understand the overall structure of the collagen molecule, think of it as the reinforcement rods called re- bar that are used in concrete construction. Indeed if one converts the molecular dimensions of the collagen molecule to measurements that we can relate to, the molecule when scaled up would measure one inch in diameter to approximately 17 feet long. Therefore, collagen is indeed nature's re-bar, because it is responsible for the strength and integrity of all of our connective tissues and organ structures. [2]
Figure 1.
The basic structural unit of collagen is a triple-stranded helical molecule. From Molecular Cell Biology by Lodish H, Berk A, Zipursky SL, Matsudaira P, Baltimore D, Darnell J. © 1986, 1990, 1995, 2000 by W. H. Freeman and Company. Used with permission.
Figure 1.
The basic structural unit of collagen is a triple-stranded helical molecule. From Molecular Cell Biology by Lodish H, Berk A, Zipursky SL, Matsudaira P, Baltimore D, Darnell J. © 1986, 1990, 1995, 2000 by W. H. Freeman and Company. Used with permission.
Basically all of the collagens share this triple-helical molecular structure as described above. However, the various other types of collagens have slightly different amino acid compositions and provide other specific functions in our bodies. Type II collagen is the form that is found exclusively in cartilaginous tissues. It is usually associated with proteoglycans or "ground substance" and therefore functions as a shock absorber in our joints and vertebrae. Type III collagen is also found in our skin as well as in blood vessels and internal organs. In the adult, the skin contains about 80-percent Type I and 20-percent Type III collagen. In newborns, the Type III content is greater than that found in the adult. It is thought that the supple nature of the newborn skin as well as the flexibility of blood vessels is due in part to the presence of Type III collagen. During the initial period of wound healing, there is an increased expression of Type III collagen. [2]
Type IV collagen is found in basement membranes and basal lamina structures and functions as a filtration system. Because of the complex interactions between the Type IV collagen and the noncollagenous components of the basement membrane, a meshwork is formed that filters cells as well as molecules and light. For example, in the lens capsule of the eye, the basement membrane plays a role in light filtration. In the kidney, the glomerulus basement membrane is responsible for filtration of the blood to remove waste products. The basement membrane in the walls of blood vessels controls the movement of oxygen and nutrients out of the circulation and into the tissues. Likewise, the basal lamina in the skin delineates the dermis from the epidermis and controls the movement of materials in and out of the dermis. [2]
Type V collagen is found in essentially all tissues and is associated with Types I and III. In addition it is often found around the perimeter of many cells and functions as a cytoskeleton. It is of interest to note that there appears to be a particular abundance of Type V collagen in the intestine compared to other tissues. [2]
Figure 3.
The intramolecular and intermolecular cross-links formed within a collagen fibril. Copyright 1994 from Molecular Biology of the Cell, Third Edition , by Alberts, Bray, Lewis, Raff, Roberts, Watson (eds). Reproduced by permission of Routledge, Inc., part of The Taylor & Francis Group.
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Figure 2.
The intracellular and extracellular events involved in the formation of a collagen fibril. Copyright 1994 from Molecular Biology of the Cell, Third Edition , by Alberts, Bray, Lewis, Raff, Roberts, Watson (eds). Reproduced by permission of Routledge, Inc., part of The Taylor & Francis Group.
Conclusion. Collagen metabolism is one of the most complex and highly regulated processes in our bodies. As we move forward in the future to design new strategies and technologies to treat the many challenging clinical problems associated with wound healing, we need to keep in mind how our connective tissues are assembled and how they are remodeled.[2]
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