Topography Of The Brain And Meninges Flashcards
What tissue is the anterior pituitary derived from
The oral ectoderm, Rathke’s pouch, part of the developing hard palate in the foetus. Rathke’s pouch eventually loses connection with the pharynx giving rise to the anterior pituitary. Anterior pituitary formed from upgrowth from the oral ectoderm of primitive oral cavity called Rathke’s pouch.
What is the posterior pituitary derived from
Nervous tissue
Has it embryological origins in nervous tissue. It’s formed from a downgrowth of the diencephalon that forms floor of third ventricle
Differences between posterior and anterior pituitary
Posterior looks very different to anterior, it contains non-myelinated axons which are the neurosecretory cells. The cell bodies of these cells are located in the hypothalamus. Anterior pituitary secretes five different types of hormone, posterior secrets two
Anterior contains acidophils and basophils which can seen by stains theirs subtypes cant be seen
Capillaries in gland are fenestrated to enable passage of hormones from secretory cells into bloodstream
Factors responsible for regulating hormone release from pituitary
Hypothalamus sends signals to pituitary to release or inhibit pituitary hormone production
Theres three mechanisms by which endocrine glands are stimulated to synthesise and release hormones: humoral stimuli (changes in extracellular fluids such as blood or ion concentration in blood), hormonal stimuli and neural stimuli
Embryological origin of brain
Adult brain develops from the neural tube in 2 key stages
In first stage the neural tube differentiates to give rise to 3 distinct primary vesicles: the forebrain (prosencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon)
In second stage the forebrain and hindbrain each differentiate into 2 further secondary vesicles while midbrain remains unchanged this results in 5 secondary vesicles of embryonic brain which then develop progressively into adult brain
What are the five secondary vesicles of brain
Telencephalon— cerebrum, lateral ventricles
Diencephalon — thalamus, hypothalamus, epithalamus, retina, third ventricle
Mesencephalon- midbrain, cerebral aqueduct
Metencephalon-pons- 4th ventricle
Myelencephalon- medulla oblongata- 4th ventricle
What are the meninges of the brain
Three layers of membranes
Protect the brain and spinal cord
Dura mater, arachnoid, pia mater
Form boundary between CNS and PNS
What is the enteric nervous system
A network of neurones found wholly within the gastrointestinal tract working to regulate its actions under the influence of both parasympathetic and sympathetic subdivisions of the ANS
What is the central sulcus
Divides frontal lobe from parietal lobe
What are sulci
A sulcus is a fissure or groove
What are gyri
A gyrus is a ridge on surface of brain
What’s the parieto-occipital sulcus
Divides parietal lobe from occipital lobe
What’s the lateral fissure/sulcus
Divides temporal lobe from rest
Frontal lobe
Function: planning and commanding voluntary movements
Landmark: central sulcus, pre central gyrus and lateral fissure
Parietal lobe
Function: sensation and perception, integration and interpretation of sensory info primarily with visual field
Landmark: between frontal and occipital lobe above temporal lobe on each cerebral hemisphere, anterior border is the central sulcus, posterior border is parieto-occipital sulcus
Temporal lobe
Function: hearing, sensory aspects of speech and memory
Landmark: middle cranial fossa, next to temporal bone, lateral sulcus, collateral sulcus
Occipital lobe
Function: visual processing area, visuospatial processing, distance and depth perception, colour determination, object and face recognition & memory formation
Landmark: posterior to parietal lobe and temporal lobe, imaginary plane in line with parieto-occipital sulcus
Limbic lobe
Functions: modulation of emotions, visceral functions, autonomic functions, hormonal functions, learning and memory
Landmark: borders corpus callosum on medial aspect of each hemisphere, surrounds rim of ventricles to brain
What is the corpus callosum
Large bundle of myelinated nerve fibres that connect the two brain hemispheres together permitting the communication between right and left sides of brain
Insular lobe
Function: associated with processing and integration of various types info including taste, visceral sensation, pain and vestibular
Landmark: deep within lateral sulcus, 5th lobe of brain, not visible from outside
What are the 4 subdivisions of the diencephalon
Thalamus, hypothalamus, epithalamus, subthalamus
Thalamus
Function: major relaying centre of the brain, its nuclei act as ‘switchboards’ controlling sensory inputs and motor outputs
Anatomical relations: located on either side of 3rd ventricle
Hypothalamus
Function: maintain homeostasis in body, energy consumption, hunger, awareness
Relations: below thalamus and anterior to thalamus
Epithalamus
Functions: to connect limbic system to other parts of brain, synthesises melatonin and enzymes sensitive to daylight
Relations: above pineal gland and posterior to thalamus
What is the limbic system
Part of brain involved in behavioural and emotional responses
Subthalamus
Functions: the subthalamic nucleus plays a vital role in the modulation of movement, helps to modulate movement through indirect pathway of basal ganglia with other compartments of basal ganglia
Relations: between thalamus and midbrain
What makes up the brainstem
Midbrain, pons and medulla oblongata
Functions of the brainstem
Houses motor and sensory pathways that act as ‘motorways’ between cerebral cortex and spinal cord
Regulates some of brains basic functions that sustain life such as breathing and regulation of heart rate
How does cerebrospinal fluid help to protect brain against injury
Acts as a shock absorber, cushioning brain and skull and spinal cord
Allows brain and spinal cord to become buoyant reducing effective weight of brain
Fluid also removes waste products from brain and helps CNS work
What is meant by hydrocephalus
Build up of fluid in the brain, excess fluid puts pressure on the brain which can damage it
It can occur by an imbalance between how much CSF is produced and how much is absorbed by bloodstream
Layers of scalp
Skin
Connective tissue
Aponeurosis-thin sheath of connective tissue
Loose connective tissue
Periosteum-dense layer of vascular connective tissue
Dura mater
First layer, cranial dura mater has 2 layers called lamellae, a superficial layer (periosteal layer) and meningeal layer
Arachnoid
Vascular, blood supply
Only layer with blood supply, fluid
Pia mater
Can’t see normally, innermost layer, composed of delicate connective tissue
