Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 12 - The Central Nervous System - Review Questions - Page 481: 30

Answer

The brain is the most important organ of the body, consequently, it is well protected. In order to get access to brain tissue, a surgeon would have to cut through the following overlying structures. 1. Skin a . epidermis b. dermis c. hypodermis 2. Muscles of the scalp or aponeurosis 3. Cranial bone 4. Meninges Cerebrospinal fluid (CSF) and brain capillaries (BBB) would also have to be moved from the area of surgery.

Work Step by Step

The structures that are external to the brain include the the integumentary tissue , aponeuroses and muscles ( over some bones). Apart from the hair, these tissues offer only minimal protection to underlying brain tissue. Hair, epidermis, dermis, hypodermis, aponeuroses, and muscles would have to be removed before getting to the real protection of cranial bones. Layers of tissues above brain tissue. 1. The skin--epidermis, dermis 2. Connective tissue 3. Periosteum( pericranium) Just exterior to the outer compact layer of the flat bones is a periosteal layer of connective tissue. Over some bones there is an aponeurosis (Galea Aponeurotica); over others there are cranial muscles. Examples of cranial muscles are the epicranius muscle, and the temporalis muscle. An example of an aponeurosis is the Galea Aponeurosis 4. Cranial bones . The cranial bones form the vault and base of the skull. These bones are the paired parietals, the paired temporals, the frontal, the occipital. the sphenoid , and the ethmoid. The calvaria which protects the front, back, top and sides of the brain comprises the frontal, parietal, and the occipital bones. These are flat bones that offer maximal protection to the brain with minimal weight, A cranial flat bone has an outer, and an inner compact layer; it also and a middle layer cancellous matrix. This kind of bone protects in three ways: a. The hard compact bone is difficult to break because of collagenous fibers and mineralized matrix. b. The cancellous bone absorb shocks. This protects against concussive injuries. The spongy bone also lightens the weight of the calvaria. into glancing blows, and lessens the impact of blows to the head.. 5. Dura mater. This issue consists of a periosteal layer that attaches the dura to the cranial bone, and a meningeal layer above the subdural space. 6 Arachnoid mater lies below the subdural space 7. Pia mater. Below the subarachnoid space is the pia mater, the thinnest, innermost meninx . After cutting through all these layers, the surgeon would finally get to brain tissue.
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