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Skin & fascia & vessels & nervous systemDr. Sabreen MahmoudLecturer of human anatomy

O B J E C T I V E SThis lecture introduces some of the basic structures that compose the body, such as skin, fascia, vessels and nervous system.Without these structures , it is impossible to describe the composition of the body.

Appreciate the general organization of the peripheral and central nervous systems.Describe the organization of the cardiovascular system.Describe the formation of lymph and its drainage into the venous system.

SkinFunctions of skin:Protection:Prevent dehydration:Sensation:Heat regulation:Excretion:

Types of skin:

Thick skin: palm of the hand & sole of the foot.Thin skin: elsewhere in the body.

Skin colourdepends on :Melanin: brown pigment.Carotene: yellow pigment.Hemoglobin: purple color.

Skin is formed of 2 parts: 1.Epidermis: Superficial epithelial layers, avascular. 2.Dermis: Deep connective tissue rich in glands, blood vessels, nerves.

Skin appendages

Hair Nail Sweat glands: = sudoriferous glands, produce sweat. They are distributed all over the skin, except lips, glans and nail bed.Sebaceous glands: secrete an oily secretion = sebum. They are distributed all over the dermis of skin, except for the palms and soles. They are abundant in the scalp and face.

FasciaI- Superficial fascia = a general coating of the body beneath the skin loose areolar tissue. It determines the shape of the body.

Distribution of FatFat is abundant in gluteal region (buttocks), front of the thighs, anterior abdominal wall, mammary gland. In females, fat is more abundant. Fat is absent from eyelids, external ear, penis, and scrotum.

Features of Superficial Fascia:

very thin on the dorsal aspect of the hands and feetIt is very dense in the scalp, palms, and soles.It contains:Subcautanous muscles in the face.Mammary glandLymph nodesNerves and vessels

FunctionFacilitates movements of the skin.Passage of nerves and vessels to the skin.conserves body heat.

Deep Fascia:

= fibrous connective tissue that surrounds the muscles, bones. It is devoid of fat, inelastic and tough.

Distributionbest defined in limbs.ill-defined on the trunk and face

Important Features1. Extensions intramuscular septa & Sheaths for vessels and nerves.2. Thickenings Retinacula.

FunctionKeeps the underlying structures in position. muscular attachmentvenous and lymphatic return.

Blood vessels

Arteries capillaries & sinusoids veins Arterio-venous connections.

1. Arteries

carry oxygenated blood, away from the heart deeply situated thick-walled, highly muscular narrow lumenValves are absentreddish in colormovement of blood giving pulseempty up at the time of deathIf injured, blood comes out like a fountain

Types of Arteries:

Large arteries = (elastic): aorta. Medium sized = (muscular): distribute blood.Arterioles: = the smallest arteries.

Arterial anastomosis Union between arteries.End arteries: arteries with no anastomosis. Ex: in brain and spinal cord, kidney, spleen.When end arteries are completely occluded, local death result.

II- Capillaries

Microscopic blood vesaels. Wall is very thin.Arterioles break into the capillaries.Form networks and unite to give small veins ( venules).Function : exchange of substances (oxygen, glucose,.......)

Blood sinusoids:

Larger than capillaries.Sites: bone marrow,.liver, spleen,...Lined by macrophage.

III-Veins

carry deoxygenated blood, towards the heart superficial and deep in locationthin-walledwide lumenValves are present

bluish in colorsluggish movement of bloodBlood in veins moves under very low pressureVeins get filled up at time of deathIf injured, blood comes out, collects in a small area

Factors Helping in Venous Return:

Overflow from the capillaries.Negative intra-thoracic pressure.Arterial pulsations .Venous valves.Muscular contractions Ex: (soleus) known as the peripheral heart.

Ill- Arterio-venous anastomoses.

connections between arterioles and venules. Sites: tips of fingers, tip of nose, ear pinna.Function : conserve body temperature.

LYMPHATIC SYSTEM

3 components: 1) Lymph vessels:2) lymphoid tissue: lymph nodes, spleen, thymus. 3) Free cells: lymphocytes and phagocytes.

Circulation of lymph:

Lymph is the body fluid which circulates in the lymph vessels.

clear, colourless and rich in protein.

Its circulation begins in the tissue spaces lymphatic capillaries. lymph nodes venous blood stream.

Lymph carries micro-organisms from the tissue fluid.

Video

Lymph vessels:

fine capillaries in the tissue spaces unite together larger vessels lymph nodes lymphatic ducts large veins in the root of the neck. The lymphatic capillaries differ from blood capillaries in the following: 1) Lymphatics have free blind ends. 2) Lymphatic capillaries have greater calibers and are irregular. 3) Lymphatics have wide pores.

Lymphatic vessels and lymphatic ducts valves flow of lymph in one direction. In the wall of the intestine called lacteals. This lymph (rich in fat) is milk-white = chyle the carrying lymph vessels = lacteals (lacteus = milky)

The lymphatic vesselsAfferent lymphatics Efferent lymphatics: At the root of the neck 2 large lymphatic ducts collect the lymph large veins. These are the thoracic duct on the left side & the right lymphatic duct on the right side

Lymphatic vessels are absent in1) Brain and spinal cord 2) Avascular structures such as the epidermis of the skin, cartilage, cornea, hair and nails. 3) Bone marrow. 4) Splenic pulp.

The flow of lymph is influenced by1) Contraction of muscles and pulsations of arteries. 2) Peristaltlc movements of the intestine. 3) Negative intrathoracic pressure.

LYMPH NODES:

oval or kidney-shaped bodies along the course of lymph vessels. present in groups.1) At the roots of the upper and lower limbs, i.e. in the axilla and the groin, respectively. 2) Close to the trachea and its bronchi.

Functions1) they are sites where microorganisms are exposed to phagocytic action by the macrophages. 2) Lymphocyte production.

Lymphocytes:1) B-lymphocytes: bone marrow, synthesizing antibodies. 2) T-lymphocytes: in the thymus (thus called T-type), and they are direct killers.

Reticulo-endothelial cells:phagocytic properties, In the lymph nodes, spleen, the macrophages are of the fixed type. macrophages may be present at sites other than the lymphatic tissue:- 1) In the liver: = Kupffer cells. 2) In the alveoli of the lung: = dust cells. 3) In the blood: = monocytes.

Nervous system

(1) Central nervous system (C.N.S.): brain and spinal cord. (2) Peripheral nervous system: peripheral nerves. 12 pairs of cranial nerves 31 pairs of spinal nerves autonomic nerves

Structure of the neuron:

The basic structural unit of the nervous system is the neuron. The neuron consists of a nerve cell and all its processes. dendrites are multiple an axon which is single, long.

Neurons are classified, into 3 types:

1) Motor neurons: skeletal muscles. 2) Sensory neurons: carry impulses to the C.N.S. 3) Autonomic neurons: stimulate exocrine glands to secrete or smooth muscles to contract.

BrainPARTS OF THE BRAIN: cerebrum, cerebellum and brain stem. The brain stem comprises 3 parts: midbrain, pons, and medulla oblongata

Ventricles of the brainCavities = ventricles filled with cerebro-spinal fluid (C.S.F.). C.S.F. circulates inside these ventricles & absorbed in the venous system.

Cranial Nerves:

There are 12 pairs a) Nerves attached to the cerebrum : * Olfactory nerve (1st cranial). * Optic nerve (2nd cranial). b) Nerves attached to the midbrain: * Ocular nerve (3rd cranial). * Trochlear nerve (4th cranial).

c) Nerves attached to the pons: * Trigeminal nerve (5th cranial). * Abducent nerve (6th cranial). * Facial nerve (7th cranial). * Auditory nerve (8th cranial).

d) Nerves attached to the medulla oblongata:

* Glossopharyngeal nerve (9th cranial). * Vagus nerve (10th cranial). * Accessory nerve (11th cranial). * Hypoglossal nerve (12th cranial).

Spinal cord

The spinal cord lies in the upper 2/3 of the vertebral canal, extending down to the level of the disc between the 1s and 2nd lumbar vertebrae. * The spinal cord is composed of spinal segments, * The grey matter of the cord is H-shaped, * The cord has a central canal.

A lateral horn is present only in the region from T. 1 to L. 2, and in the sacral region corresponding to S. 2, 3, 4.

(T. = thoracic ; L. = lumbar; S. = sacral).

The function of the nerve cells :

1) Anterior horn: motor. 2) Posterior horn: sensory. 3) Lateral horn: autonomic (sympathetic or parasyrripathetic).

Anatomy of spinal nerve:

31 pairs of spinal nerves : 8 cervical nerves:12 thoracic nerves: 5 lumbar nerves: 5 sacral1 coccygeal nerve Each spinal nerve arises by 2 roots: one dorsal and one ventral.

1) Dorsal root: sensory or afferent. - It has a ganglion = dorsal root ganglion.

2) Ventral root:

motor or efferent. - Its fibers arise from the anterior horn cells (A.H.Cs ). - Its fibers also include the preganglionic autonomic. * The dorsal and ventral roots join each other to form the trunk of the spinal nerve. the trunk divides into 2 primary rami (anterior and posterior)

1) Anterior primary ramus:

- form plexuses. - A sympathetic ganglion is attached to the anterior primary ramus by (one white ramus which is myelinated and one grey ramus which is nonmyelinated).

2) Posterior primary ramus:

It supply the muscles and skin of the back.

DERMATOMES: Each strip of skin is supplied by spinal nerve, GANGLIA: a collection of nerve cells situated outside the central nervous system. Nucleus: a collection of nerve cells present inside the C.N.S.

Classification:1) Sensory ganglia: attached to the dorsal roots of spinal nerves = dorsal root ganglia. 2) Autonomic ganglia: sympathetic ganglia & parasympathetic ganglia

Rami of sympathetic ganglia:

1) White ramus communicans: is myelinated = preganglionic. 2) Grey ramus communicans: is non-myelinated = postganglionic.

Autonomic nervous system

1) The sympathetic stress and strain (as in fight and flight). 2) The parasympathetic part rest and relaxation (as in sleep).

(autonomic = self-controlling). Its higher center is represented by the hypothalamus.

The sympathetic ganglia are situated close to the vertebral column, the parasympathetic ganglia are embedded in the walls of viscera.

Distribution of sympathetic fibres:1) The preganglionic sympathetic fibres : a - relay in ganglia in the sympathetic trunks. b - relay in the medulla of the suprarenal gland.

2) The postganglionic sympathetic fibresa - To exocrine glands. b- To walls of viscera. c - To heart. d - To blood vessels (vasomotor). e-To skin (motor).

MeningesDura mater: Arachnoid mater: Pia mater:

The 3 meninges are separated

1) Epidural space: 2) Subdural space: 3)Subarachnoid space: contains the C.S.F & blood vessels.

Thanks Dr. Sabreen