Medical Textile Materials

Yimin Qin

• Publisher: Woodhead Publishing
• Year: 2015
• ISBN:
  9780081006245
• Topic: Medicine
• Subtopic: Biotechnology in Medicine

Medical Textile Materials provides the latest information on technical textiles and how they have found a wide range of medical applications, from wound dressings and sutures, to implants and tissue scaffolds. This book offers a systematic review of the manufacture, properties, and applications of these technical textiles.

After a brief introduction to the human body, the book gives an overview of medical textile products and the processes used to manufacture them. Subsequent chapters cover superabsorbent textiles, functional wound dressings, bandages, sutures, implants, and other important medical textile technologies. Biocompatibility testing and regulatory control are then addressed, and the book finishes with a review of research and development strategy for medical textile products.

• Provides systematic and comprehensive coverage of the manufacture, properties, and applications of medical textile materials
• Covers recent developments in medical textiles, including antimicrobial dressings, drug-releasing materials, and superabsorbent textiles
• Written by a highly knowledgeable author with extensive experience in industry and academia

1

A brief description of the human body

Abstract

Medical textile materials are used in various parts of the human body either to restore functions or to enhance performance, and the interaction between the materials and the underlining body parts is critical to therapeutical success. This chapter describes the physical and biological structures of the human body, outlining the various systems within the body as a whole and the anatomical structures. The skin and cell structures are also outlined, with a view to illustrate the physical composition of the human body at the four main levels: cells, tissues, organs, and systems.

Keywords

Anatomical structure; Cell structure; Human body; Skin structure; Tissue structure

1.1. Introduction

The human body is the entire structure of a human organism and consists of almost 100 trillion cells. It is arguably the most complex structure on earth, with billions of microscopic parts, each with its own unique identity, working together in an organized manner for the benefit of the total being. Macroscopically, the human body is a single structure built from billions of smaller structures of four major kinds—cells, tissues, organs, and systems—which are organized biologically to form a whole body comprising head, neck, torso, arms, and legs. The average height of a man is about 1.7–1.8 m, while the height of an average woman is about 1.6–1.7 m. The size, type, and composition of the human body are firstly determined by genes and secondly by postnatal factors such as diet and exercise.

1.2. The systems within the human body

Many diversified activities of men and women are carried out through the combined actions of a complex structure of organ systems distributed in different parts of the human body. These include the musculoskeletal system, cardiovascular system, digestive system, endocrine system, integumentary system, lymphatic system, immune system, respiratory system, nervous system, urinary system, and reproductive system.

Musculoskeletal system: The human skeleton is usually composed of 206 distinct bones, including 26 bones within the spine and vertebral column, eight bones in the cranium, 14 bones in the face, 26 bones in the hyoid, sternum, and ribs, 70 bones in the upper extremities, and 62 bones in the lower extremities. These bones attach to other bones by joints, while the skeletal muscle attaches to the skeleton by tendons. The body is made up of three types of muscle tissue: skeletal, smooth, and cardiac muscles. Each of these has the ability to contract and expand, which allows the body to move and function.

Cardiovascular system: The cardiovascular system comprises the heart, veins, arteries, and capillaries. It is responsible for the circulation of blood, through which oxygen and vital minerals are distributed to the tissues and organs that comprise the body. The main part of the cardiovascular system is the human heart, which is divided into three layers called the endocardium, myocardium, and epicardium, each with a different thickness and function. The left side of the heart is responsible for pumping blood to all parts of the body, while the right side pumps only to the lungs for reoxygenation of the blood.

Digestive system: The digestive system is responsible for processing food and transforming nutrients into energy. It consists of the buccal cavity, esophagus, stomach, small intestine, and large intestine, ending in the rectum and anus. These parts are combined together to form the alimentary canal or the digestive tract.

Endocrine system: The endocrine system is made up of a group of glands that produce the body’s long-distance messengers or hormones. Hormones are chemicals that control body functions, such as metabolism, growth, and sexual development. The glands, which include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, thymus gland, pineal body, pancreas, ovaries, and testes, release hormones directly into the bloodstream, which transports the hormones to organs and tissues throughout the body.

Integumentary system: The integumentary system includes the skin and skin appendages, such as the sweat and sebaceous glands, hair, and nails. As the largest organ system in the human body, it is responsible for protecting the body from most physical and environmental factors.

Lymphatic system: The main function of the lymphatic system is to extract, transport, and metabolize lymph, which is the fluid found in between cells. It is a defense system for the body, filtering out organisms that cause disease, producing white blood cells, and generating disease-fighting antibodies. It also distributes fluids and nutrients in the body, and drains excess fluids and protein so that tissues do not swell. The lymphatic system is made up of a network of vessels that help circulate body fluids. These vessels carry excess fluid away from the spaces between tissues and organs and return it to the bloodstream.

Immune system: This system is responsible for protecting the body from infections and diseases. It is composed of leukocytes, tonsils, adenoids, thymus, and spleen.

Respiratory system: This system comprises the pharynx, larynx, trachea, bronchi, lungs, and diaphragm. It is responsible for inhaling air into the human body and removing carbon dioxide from the body.

Nervous system: The nervous system consists of cells that communicate information about an organism’s surroundings and itself. It is made up of the brain, the spinal cord, and nerves. By sending, receiving, and processing nerve impulses throughout the body, the nerve system regulates the muscles and organs to respond to the external environment.

Urinary system: This system includes the kidneys, ureters, bladder, and urethra. It is responsible for eliminating waste from the body, in the form of urine.

Reproductive system: The reproductive system allows humans to produce children. A sperm from the male fertilizes the female’s egg, or ovum, in the fallopian tube. The fertilized egg travels from the fallopian tube to the uterus, where the fetus develops over a period of nine months.

1.3. Human anatomy

Human anatomy is concerned with the study of the human body in its macroscopic and microscopic forms. Macroscopically, the morphology of the human body can be seen by the naked eye, and gross anatomy studies anatomical structures concerning organs and organ systems. Microscopic anatomy is the study of minute anatomical structures assisted by microscopes, generating information on tissues and cells in the human body. Histology and cytology are concerned with tissues and cells, respectively.

The history of anatomy has been characterized by continually developing understanding of the functions of organs and structures in the body. Methods in this field have advanced dramatically, from examination of animals through dissection of fresh and preserved cadavers to technologically complex techniques developed in the twentieth century. The studies on human anatomy have generated a comprehensive understanding of the human body, which is important for medical professionals such as physicians, dentists, physiotherapists, nurses, paramedics, and radiographers in their work.

In general, the human body comprises a number of regional groups.

1. Head and neck, including everything above the thoracic inlet, such as brain, eye, pineal gland, pituitary gland, thyroid gland, and parathyroid gland.

2. Upper limbs, including the hand, wrist, forearm, elbow, upper arm, and shoulder.

3. Thorax, which is the region of the chest from the thoracic inlet to the thoracic diaphragm, and contains the heart, lungs, esophagus, thymus gland, and pleura.

4. Human abdomen to the pelvic brim or pelvic inlet, containing the adrenal gland, appendix, bladder, gallbladder, large intestine, small intestine, kidney, liver, pancreatic gland, spleen, and stomach.

5. The back, including the spine and its components, such as the vertebrae, sacrum, coccyx, and intervertebral disks.

6. Pelvis and perineum. The pelvis consists of everything from the pelvic inlet to the pelvic diaphragm. The perineum is the region between the sex organs and the anus.

7. Lower limbs, including everything below the inguinal ligament, including hip, thigh, knee, ankle, and foot.

1.4. Skin

The skin is the outer covering of the human body: it has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments, and internal organs. For the average adult human, the skin has a surface area of 1.5–2.0 m², most of it 2–3 mm thick. The average square inch or 6.5 cm² of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1000 nerve endings. In addition, the skin provides a rich and diverse habitat for bacteria, which number roughly 1000 species from 19 phyla.

1.4.1. Skin structure

Overall, the skin is composed of three primary layers: the epidermis, which provides waterproofing and serves as a barrier to infection; the dermis, which serves as a location for the appendages of skin; and the subcutaneous layer, also called the hypodermis.

1.4.1.1. Epidermis

The epidermis is the relatively thin, tough, outer layer of the skin, and comprises cornified, translucent, granular, spinous, and basal layers. It contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The main types of cells in the epidermis are Merkel cells and keratinocytes, with melanocytes and Langerhans cells also present. Most of the cells in the epidermis are keratinocytes. They originate from cells in the deepest layer of the epidermis, that is, the basal layer, and slowly migrate up toward the surface of the epidermis. Once the keratinocytes reach the skin surface, they are gradually shed and replaced by newer cells pushed up from below. During this process, the cells change shape and composition as they die due to isolation from their blood source. From the basal layer to the corneum, the keratinization process takes place in about 27 days.

1.4.1.2. Dermis

The dermis is the layer of skin beneath the epidermis and is tightly connected to the epidermis by a basement membrane. It harbors many mechanoreceptors and nerve endings that provide the sense of touch and heat. In addition, the dermis contains hair follicles, sweat, sebaceous, apocrine glands, and lymphatic and blood vessels, contained in a thick layer of fibrous and elastic tissue made of collagen, elastin, and fibrillin, which give the skin its flexibility and strength. The sweat glands produce sweat in response to heat and stress, while the sebaceous glands secrete sebum into hair follicles, which keeps the skin moist and soft and acts as a barrier against foreign substances. The blood vessels of the dermis provide nutrients to the skin and help regulate body temperature. Heat makes the blood vessels enlarge (dilate), allowing large amounts of blood to circulate near the skin surface, where the heat can be released. Cold makes the blood vessels narrow (constrict), thereby retaining the body’s heat.

1.4.1.3. Subcutaneous layer

The purposes of the subcutaneous layer are to attach the skin to underlying bone and muscle, and to supply it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cells in the subcutaneous layer are fibroblasts, macrophages, and adipocytes.

1.4.2. Functions of the skin

As it interferes with the external environment, the skin plays a key role in protecting the body against pathogens and excessive water loss. The main functions of the skin include the following.

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Table of contents

• Cover image
• Title page
• Table of Contents
• The Textile Institute and Woodhead Publishing
• Copyright
• Woodhead Publishing Series in Textiles
• Preface
• 1. A brief description of the human body
• 2. An overview of medical textile products
• 3. A brief description of textile fibers
• 4. A brief description of the manufacturing processes for medical textile materials
• 5. Applications of advanced technologies in the development of functional medical textile materials
• 6. Superabsorbent polymers and their medical applications
• 7. Functional wound dressings
• 8. Medical bandages and stockings
• 9. Surgical sutures
• 10. Textiles for implants and regenerative medicine
• 11. Antimicrobial dressings for the management of wound infection
• 12. Medical textile products for the control of odor
• 13. Medical textile materials with drug-releasing properties
• 14. Biocompatibility testing for medical textile products
• 15. Regulatory control of medical textile products
• 16. Research and development strategy for medical textile products
• Index